That's a bummer that he's not taking Trinity, I bet she would have loved it. Maybe next time!!! I do not in any way mean to defend your ex, however, maybe it's something they've always wanted to do on their own, just the two of them. Sometimes it's fun for adults to do kid-type stuff, but on their own...remember that Disney is geared at adults too, with beer gardens and other more adult activities. As you said, it could also be that they are doing other things while they are on vacation that aren't suited to children, and he may be only looking out for her best interest-she might be bored with the other things they're doing, and he may not want to put her (or himself) through a bored to tears 6 year old
I know you would never leave her out of something as fun and cool as Disney, you'd probably save it for another time when she could join you- you're a great mommy!