I agree with Machka's advice about staying on the coastal road (highway 19a) It's really beautiful and has a lot of camp grounds along the way.
Also, there is a REALLY good barbecue stand on the South end of Parksville with real pit barbecues. It's cheap and super filling. The ribs just fall off the bone. Don't miss it. They're there from 11am - 5pm I think
Port Alberni has a few good restaurants right downtown. One of them has good barbecue sandwiches (try the pulled pork) and is worth the small detour. I'm not sure what the camping situation is like on Highway 4 out to Tofino but if you want to wild camp there are lots of places once you get past Port Alberni. You just have to go down a logging road far enough to escape the road noise and throw your tent up in the woods.
I think the only camping near Tofino is in the National Parks about 50kms away from Tofino. Inquire about it at the tourist information centre at the junction of highway 4 and the road that goes to Uclulet. You can probably reserve a site there, they have a lot of good information on things you can do too
Don't go to any of the restaurants in Tofino unless you are desperate, they are expensive and not very tasty and the portions are small. The grocery store right downtown has a lot of good food like smoked salmon and roasted chicken, good assortment of cheese and veggies too. Way cheaper and more satisfying.
The roads on Vancouver Island are good, not great but you will have no problems on racing bikes. On Highway 4 between Parksville and Tofino there are some very narrow sections of road with no shoulder so you will have to ride in the same lane as cars. These sections are NOT wide enough to accommodate a bicycle and two cars beside one another so you will have to listen for cars and ride through them very fast. Those same sections tend to be bordered by cliffs and a guardrail preventing people from driving into the lakes beside the road. People on that stretch of road drive foolishly and don't tend to know what to do when they encounter bikes in that situation so be very alert!
In Courtney get food if you need it before you head out to the ferry because there's little available on the way (one gas station with snacks IIRC). Powell River has its main commercial district (and best restaurants, coffee shops and grocery stores way up the hill from the area near the ferry terminal. If you need anything at all you'd better buy it in Powell River because although there are some stores on the way to Saltery Bay, they have a limited selection and may not be open. There are some commercial campsites just outside of Powell River but after that I'm not sure, I don't pay to camp if I can avoid it so I don't pay attention to those campgrounds usually. I'm sure if you ask anyone they will be able to show you one. Or you could find a place to throw your tent up most places if you're desperate for sleep.
After Earls Cove you'll see a turn off to go into Egmont, there's not really much interesting about Egmont but if you're there at the right time there's the Skookumchuck Narrows which has some big tidal whirlpools and standing waves.
I don't know anything about Spipyus Park but I suggest you find out about it before you go. It's entirely possible the road in is not paved.
If you find yourself wanting to camp near Sechelt there's a nice campground with showers at Porpoise Bay just 10 kms NE of town. Davis Bay between Sechelt and Roberts Creek is really nice, good scenic view with large tidal flats in case you want to squish sand between your toes.
There's a provincial campsite in Roberts Creek that has showers, never stayed there but it's probably the best option in the area.
In Gibsons, if you don't need to buy anything I highly suggest you make a right turn on Pratt Road at the Northern part of the town and ride all the way down to the low level road beside the ocean. The road is excellent, not heavily traveled and there's a place called Gospel Rock that you can climb out on and get a good view of the ocean and surrounding islands, beautiful Arbutus trees too. there are some shops and restaurants further on in Lower Gibsons and after that it's a few kilometers to the ferry via a pleasant highway.
If you go through upper Gibsons you have three choices of the route to take to the ferry and they all involve fairly steep hills. School Road (just after the elementary school on the right) is around a 17% grade with lots of traffic and best avoided. Hwy 101 is not as steep but it's busy and the shoulder is usually covered in gravel and a bit narrow. If you want to ride it you'll have to block traffic in places and fly down without brakes on, probably not your idea of fun. The route direct to the ferry via North Road is kind of boring but the last part has a nice wide road with 2 lanes going in each direction and a shoulder. The hill right before the ferry is pretty steep though you could get going over 80 km/h on it with touring bikes I think. Your choice.
Can you tell I used to live in Gibsons?
Hope you have fun