I think you both should go to WDW. It's not at all selfish for you to suggest going back this year. I mean he should keep in mind that you accompany him to his tattoo conventions. Would it be so terrible for him to do something you want to do? And besides, WDW is the happiest place on eart. I can't imagine that he had a bad time the last occasion you guys went.
I also took my then boyfriend to WDW in March 2001, for his first trip to WDW (it was like my 5th time). And he LOVED it! Since that time, we have gotten married and have a daughter that we are taking to WDW in about 3-4 weeks!!! Disney is a magical place.
You can probably convince him by spicing up your trip. Do something you guys didn't do last time. Also try looking at giftsofalifetime.com, do something special for him so he'll appreciate the trip even more, and see that it's not all about you. It's about being together! Good luck!