Well I don't really have any advice on how to convince them. Maybe you can bribe them a little... I know it would work for me
I see quite a few saying they think it has to do with childhood memories, growing up Disney, or things similar. But I don't think that is always the case. For instance, I've only been to Disneyland twice; once when I was about 6 and once for my Grade Nite 12 years ago. And all this time I've lived only about 90 minutes away!
We are about to get SoCal AP and I'm very, very excited. It will be the first time my husband has gone since 20-some years ago, and we want the WHOLE EXPERIENCE I want to slow down, take it all in, look at everything and just soak in the magic that is Disneyland. I want this to be our special thing we do together to enjoy it and make some magic (for lack of a better word). So to be honest, I think wanting the whole experience versus running to every thrill ride comes with age. Also, when you have to pay for your own tickets, food, and souvenirs, that tends to make you look at things differently and appreciate it.