My first long-distance 2-day bicycle ride this weekend (need some advice)
 

This weekend I will be doing my first long-distance group bicycle ride along the California coast
It's a bicycle ride for charity http://www.hazon.org , not a race. Each day I have the option to do either a 30 mile or 55 mile route.
Both will have some medium-challenge hills. This will be the most intense amount of bike riding I have ever done.
I've been car-free for the past year and ride between 10-30 miles each day. But I rarely have to deal with any hills
or challenging inclines on my rides and I didn't have much time to train for hill endurance.
My daily mileage is also spread out throughout the day, where this upcoming 30-55 miles per day will be done with only a
few small rest stops in between. Naturally I'm a bit apprensive about my physical endurance for this race.
I want to do the 55-mile route each day, but I'm concerned I won't have the endurance especially the hills.
Even the hills on the 30-mile route would be a major concern.
I also don't know if it's actually necessary to do a 55 mile ride during my training period to be able to do a 55-mile route for the bicycle ride event.
But I know I'm probably in good shape relative to others doing this ride, since I don't think that many of them ride the distances I do
each and every day for over a year. For optimum performance this is my plan
Stretch before and after the ride, and stretch at the scheduled rest periods
Pop a GU gel packet every 45 minutes (I may keep one taped with a ziplock onto my bike so I can gulp while riding)
Drink plenty of water before, during and after my ride each day
Pop a small can of Starbucks doubleshot espresso for a caffeine kick as needed
May bring my headphones and MP3 player so I can use music to motivate me

If anyone has some additional advice, please share it.
Thanks

Forget the headphones. Cycling is hazardous enough without music in headphones causing you to miss the sound of an approaching car.

You really have to quantify what "hills" mean. My personal worst was 3200 ft up in 12 miles with only 150 feet going down at the end of a 50 mile day. It took over 3 hours with full camping gear on the back. I doubt, if you will have anything approaching that ordeal.

If you are really want to "cheat" on hills, go as slowly as you can in your lowest gear up the hills. That lowest level effort should enable you to avoid bonking out by going too fast.

If you're feeling apprehensive, go for the shorter route the first day. If you are riding 30 miles on a regular basis then personally I would try the longer route. You might surprise yourself. Every uphill has a downhill that you can coast. And there are bound to be flats in between.

As far as food goes, I'd eat a bit more than just a gel every 45 minutes. The ride has rest stops every 15-20 miles. Stop and get something to eat, and get off the bike for a bit. A little break from the saddle can make a big difference during a long ride.

You don't need to ride 50 miles beforehand. Just pace yourself and ride at a relaxed pace and you will be fine.

It sounds like a nice ride for a great cause.

I'm confused about your link, there are multiple rides. Maybe I've ridden too much in my lifetime to have the proper perspective, but I can't see how 30 miles a day requires any preparation whatsoever. 55 miles in a day is similarly fairly easy given the existence of even a single rest stop en route. If I'm riding thirty miles, I might not bother to take food. There is a 50 mile ride around here with a lot of climbing that requires some amount of food, 3 cliff bars for example. However, that's an exception, and even on that ride I don't stop. When I was a teenager, we called 60 mountainous miles a "one banana" ride. Of course, if you are doing a long distance ride, i.e. 100 miles minimum, more food is required starting earlier in the ride.

Your daily riding is probably adequate training for the double 55. If you're riding 30-30 comfortably, you can go 60-60.

To increase your endurance: Take off 1 or 2 mph from your training pace. Spin up the hills in a low gear, and they won't impact you as much. Take a supplement like Endurolytes to prevent cramping.

Good luck, and +1 on ditching the headphones; I'd be surprised if the ride allowed them, anyway.

Stretching is optional (depends on the person, if you don't normally stretch before riding, no reason to start now). Some people swear by it, I've never seen the need, myself.
Gu is optional. Normally, at organized rides, they'll have bananas and cookies and stuff, and that's all you really need.
Water varies. If it's hot, try to get plenty of electrolytes to help avoid cramping, rather than just water. If it's not hot, just drink when you get thirsty. (Stopping to pee every half hour won't help you any.) At the organized rides around here, they tend to have Poweraide that tastes like it's really watered down, so consider taking your own electrolyte powder or tablets if you have muscle-cramping problems.
I drink coffee at work all the time, but never had any reason to take any with me on a ride. Maybe if I was riding 24 hours straight or something.
Skip the headphones. I don't want them, I assume everyone is like me, so therefore, you shouldn't want them either, that's how the logic goes there. Actually, some people use them, some don't. If I was riding an unfamiliar ride with a lot of people, I'd probably skip 'em so I could hear the occasional "Car back!" or "On yer left!" or to carry on conversations with other riders, which does happen on occasion.
On the hills, it can be tempting to power your way over them, which can give you toasted legs in short order. So just keep pedaling at a comfortable speed, downshift as required so you're not working much harder than on level ground, and you should be okay. If you get into your lowest gear and can't move, it's time to walk up the hill- but that very seldom happens on public roads. If you're going uphill and your legs are just getting too tired or you're getting too out of breath, just stop and rest a minute and then ride on again, slower, as opposed to walking up the hill.

Consider your weight and average speed as well. If you're in reasonable shape and zipping around on the flatlands at 18 mph average, you probably won't have any issues doing 55 miles in hillier country, although it might be slower. If you're overweight and averaging 12 mph on the flatlands, be prepared for some challenges out there.

On a lot of the 1-day charity rides, they will have multiple distances, but nobody cares if you switch halfway through. Look at your route maps; they may allow you to get 20 miles out before you have to decide on the longer or shorter distance. If they have different maps for the 2 courses, just ask for one of each.

Get a motor for the bike?