IMHO, since you worked hard for the trip you should enjoy it - no guilt - no pressure - just go and be a kid. If the older boy doesn't want to go - don't force it. If you let him stay home graciously, you will build far more bonds between you than if you force him to go! If your dh answers that he'd really rather stay home, again, I'd let him, graciously. He may know best what kind of relaxation he needs. If the younger son wants to go, take him. If he doesn't - you go anyway. Grab a girlfriend to go with you - or NOT. you can still have a super fantastic time doing what YOU want to do when you want to do it. It won't be the trip you dreamed of, but it can be a good trip anyway.
Very often our dream trips don't turn into reality, even if everyone goes! that was my first trip - I dreamed it would be fun, romantic. HAH! The first trip my husband and i went, he was a grump. Just AWFUL. I swore I'd never vacation with him again.
About 4 or 5 years later, when I graduated college (at 50), I celebrated by going to the world with my girlfriend. we had a great time. Then I got involved with a Disney website and started going more and more often. Every trip was so much fun. FINALLY, my husband asked to go with me, and believe me he was good as gold on that trip! Put himself out to be charming, even. Well, now I let him go once in a while - but i'd still rather go alone or with girlfriends!