training plans and vacation

at the end of this month i will be starting a 12 week olympic training plan for a tri in september. however, in looking at it, we will be on a cruise during week 3 of the training plan (approx. 8 hours of activity) with a recovery week (approx. 4 hours of activity) for week 4, which is the week after the cruise. will i totally disrupt the plan if i flip flop those weeks? i don't mind doing some training while i'm gone, but i worry that i won't have either the time or the motivation to get the full 8 hours done. my next scheduled recovery week is week 8. having never really followed a plan before i'm not sure how flexible i can be with it. 

also, getting the swim portion in won't be a problem, and the run i can do on the treadmill if necessary, but what about the bike? will it be alright to use just a regular stationary bike during that time? i know it's not the same as a trainer or being on the road, but i suppose it's better than nothing. there are also spin classes available on the ship, so i thought that might be a possibility as well.

any advice would be appreciated!