Unfortunately, no, no kids will be allowed at any events. However, Disney offers childcare services through Kids Nite Out - please contact them at 407-828-0920 or https://kidsniteout.com/ to make accommodations. The wedding will also be at the Swan Reserve, and there is a Camp Dolphin available across the street until 10pm - you can read more here: https://swandolphin.com/activities/kids/camp-dolphin/
For the actual wedding and reception, no you do not. If you are attending the Bachelorette party you will need a 1 day park hopper ticket. However, if you are planning on going to a park more than once, tickets are less expensive per day the more days you purchase. If you'd like to reserve specially priced tickets, please do so here: https://disneyworld.disney.go.com/reservations/bolt_wdw_wed_00001/
We are aiming for semi-formal! You are welcome to also dress as your wedding-inspired favorite Disney Princess or Prince!