In short: lovely! High temp around 80, overnight low of upper 40s, which is a little extra chilly in the desert.
Something you like dancing in! Wedding day events will be outdoors on uneven terrain so footwear you're steady in is a good idea. The evening will cool off so you may want a layer to wear.
When coming into Catalina State Park, you will come through a ranger station. The ranger will direct you to the Gila Monster & Ringtail Group Sites where you can park for the afternoon and evening. Those coming to camp overnight can park here, too.
The Arizona State Parks website has a lot to offer if you want to know more about trails, geology, ruins, or park history! https://azstateparks.com/catalina/