TMQ,
Everyone is different. It might be a good idea to get yourself into an environment that has some of the same issues before you take the trip.

For example, if you are not comfortable shopping at the grocery store on a croweded day, you probably aren't ready for Disney. You simply won't enjoy it.

I just started swimming and I found that I am okay on a weekday, but on a Saturday when there are a lot of screaming kids I am pretty useless and afterwards I am stressed. You might try going to a local pool on a weekend and see how you do. Or try visiting a small carnival.

If you decide to go to the amusement park and you are immediately uncomfortable just leave. Go to the beach. Do something enjoyable instead. Vacations can be stressful. You can minimize the stress by planning ahead and making contingency plans well in advance.

Have fun.
Gil