I think deep down you do "get it" you just don't want to because you love Disney so much. Understandable. However, think of it this way, you raised young adults who will speak up for themselves. May not be what you want to hear, but you didn't raise milquetoast.
When you do talk with them make sure you stand by your word that you will let them do their own thing. Don't make them feel guilty for not going to rope drop.
We do this on cruises with my dd. I know she doesn't want to hang out with adults all day on the ship, so she takes off with her friends (they initially meet day 1 in teen club, but then venture all over.) Our only caveat is meeting for dinner and abiding curfew. It becomes a win/win since we all have fun and no one is complaining.
Whatever they decide, I am glad you aren't forcing them to go. That just makes for a miserable and expensive trip.