I've been to a handful of munches, some in Atlantic Canada, where I am currently and some back in Toronto. Munches vary greatly depending on region and how big of a scene there is in your neck of the woods.
The munches in Atlantic Canada are small, intimate affairs. They're usually held at bars that have been rented out for the evenings. One of the things that I like about these munches is that you make more meaningful connections with people, I've made a few friends through these local munches. Another interesting thing is because there aren't a heck of a lot of AB's in Atlantic Canada, people from other fetish subcultures and alternative walks of life come to the munch as well. I've met people at local munches that were into BDSM, other types of role play and even just a few regular vanilla folks who thought the ABDL scene/lifestyle sounded interesting and cute.
The larger the city, however, the larger the community and the more populated the munch. I went to a Munch in Toronto and it was reasonably packed. It was a different climate, kind of clique, most of the people there already had a Mommy or a Daddy and there were very few newbies. They also didn't have anyone around who was willing to introduce a new AB's to friends and other seasoned members of the community, you were pretty much on your own. It was fun, I struck up some conversations, but from experience, smaller, more intimate munches are where it's at.
Oddly enough, I've never attended a munch at a theme park, that sounds very fun and like a much more enjoyable place to have a munch than some dive bar. I've never been one for the bar scene, so I always feel a little bit weird when talking to other AB's in a bar room setting, after all, babies don't drink
In any event, I hope you have fun. Some more advice, try not to be overly eager, strike up conversations when you see an opening or let people come to you. Also, try not to be nervous, nerves are never fun. Even though this will likely be a new experience, there's no reason to tense up, everyone at the munch is there for a similar purpose to connect and have fun with likeminded people. Go to your munch with your head held high and be ready to engage in conversation when the opening presents itself and you might just meet some new padded friends, I even know some people who met their Mommy/caregiver/partner through munches, although that seems to be quite rare. Once again, have fun