WOW - I just looked at the OPs website through her link...this girl is no slacker. She volunteers heavily and is ridiculously active in her community. I imagine she and her Fiancee are ready for a break. Passing the Bar is no small task - my DH took a long trip after he passed his. That is pretty normal. She also plans on going to med school but it appears she is waiting until it makes financial sense to go once her fiancee is working.
I don't think this is a matter of a lack of money. I think the OP is stressed about not knowing where they will be living and what her future holds. Which is a very normal reaction for someone her age. Change is scary - no matter how good it might be. She loves where she is now and the thought of taking on a new chapter in her life must be a little scary.
OH - and her fiancee's family seems to be the root of their Love for Disney

I doubt they are upset they are taking the trip. Her FFIL is probably just figuring in this housing market that he should get the house ready and on the market since it will probably take a while to sell.
OP - enjoy your trip. What you have coming might be scary - but it will be wonderful too!