I've refused to go to all my siblings graduations. I got out of the last one by volunteering to watch my cousin while my Uncle and Aunt went.
Hmm... my DH wouldn't let me go to
Disneyland Paris when we were there a couple years back either. He wasn't my DH yet though. He used the rationale that his first Disney experience should be at the real thing. The only reason I let him get away with it was because we were only there for a couple days, and the tickets to Disneyland would have been expensive.
Personally I find Disney much less stressful than Europe, but we were also completely broke when we were there, so I couldn't plan as much in advance as I wanted to... The only reason I got to go to Paris was that my parents and grandparents sent money for my birthday.
Definitely research the various deals available, and you might be able to make both trips work. Europe is expensive and there's no way to guarantee the level of customer service that you get at Disney.