I use that standard Campy triple you have with a 13/29 cassette and a medium cage RD on most of my bikes. I do lots of big climbs followed by longish descents. It's a good combo as-is, and will most likely be just the thing for the trip you have planned. Campy does make a 53/40/30 triple - I have one on my Cinelli. But I don't think it's worth swapping out the middle ring if you already have a triple in-hand.

I also have an IRD 11/34 cassette on one of my bikes, but I'm hesitant to recommend it. The thing I don't like is that is goes from 28 to 34 on the last two cogs, so if you are struggling a little bit on the 28, your only two choices are to keep struggling or totally bail to the 34. Plus, you'll need a long cage RD.

I really don't think you have to fret with this - go the simple, factory route and just get a 13/29 cassette and be done with it. You'll have all the "normal" gears you're used to, and the low gears for when you're getting gassed or just want to take it easy. I think you'll find that you'll spend the majority of your ride on the 42 in front, just working up and down the cassette as needed. Makes life simple.