October Temps for Mickey's Not-So-Scary?

We'll be going to the party in early October and I'm trying to plan our costumes but have no idea how hot it'll be during the party. When I was looking up temps online I read anywhere between 70-85, but I'm guessing those are highs for the day? My toddler wants to be Zero so my husband and I would be Jack and Sally, but for sure my toddler and likely my husbands costumes would be long sleeve and I'm not sure if that'd be too hot then with the temps. We did talk about Finding Nemo/Dory characters as those are his favorite movies so I'm wondering if that would be a better choice since those could be more hot weather friendly.