My husband had RNY in June 2006. We had committed to chaperoning a bunch of high school kids to Europe (he teaches European History). His surgeon said 6 weeks was the soonest he could go and we went 6 weeks to the day.
1. walk a lot on the plane. DVT, blood clots are still a risk. My husband wouldn't, he wiggled his feet, and he had a big bruise on his calf when we landed in London. He was very stupid, stubborn and lucky.
2. Walking a ton: no problem, stay hydrated
3. 23 mile bike ride. tough call. You'll have been biking up till this so you will have an idea if you can handle this or not
4. eating: the biggest challenge. My husband was still having to concentrate very hard when eating or he'd hurl. So he wasn't mr. sociable fun guy at meals. And there was the infamous incident at a McDonalds near Covent Garden when he was puking up his fish and chips very loudly while 6 schoolgirls waited to use the bathroom. We ran out of there.
If he was careful, he didn't have problems, but he had to concentrate.
Later on in your life you will probably be able to have shaved ice and stuff but I wouldn't risk it now if I were you either!
I brought some nuts, nut bars, and jerky along for protein in case he needed it and he kep****er on hand constantly.
the 23 mile bike ride is the only thing I would worry about in your case. but you'll know. have fun!
edited to add: he also brought t shirts and underwear he didn't care about and threw it away every night since he was losing. The hotel staff in Paris kept yanking his clothes out of the trash because they probably figured he was a really stupid America! Gave him lots more room in his suitcase!