Ok...
I would hire a bouncy castle or a decent animal entertainer.
Hire hall for an hour - hour and a half for the party. If you have 2 adults I'd say half an hour for clear up. Set up I'd say half hour to put the tables together for lunch. Blow up castle. Put banners/balloons up. More hands the better setting up!
The food I would do them all a box of food. A sandwich (when you get invite responses ask if their dc would like ham/cheese/jam). A bag of crisps. A kinder hippo. A bag of haribo. A drink of fruit shoot (lids taken off before)
Maybe quiche and ham rolls, tea/coffee for parents.
Invites out a good two weeks before (I try and do 3 weeks). If you're aware of siblings that might want to come/toddlers mums might have to bring....you need to know so you can do them a box of food. Unless they're not welcome in which case you need to make that clear. Parents and siblings tend to join here but where we used to live parents dropped and ran.
Maybe say kids can be in fancy dress if they want to?
You will need someone supervising the castle if you get one.
Lots of balloons! On walls. On the floor. Kids will play with balloons for ages! Blow them up the night before and take them in black bags. I use ribbon to fasten 2/3/5 together to put on doors/walls. Individual on the floor.
Food can be made earlier in the day and put into the boxes-have them named.
Small Batman cake/napkins/cups for jugs of juice-it will be needed if you get a bouncy castle.
I would do individual cupcakes in individual cardboard boxes with a tag on them saying "thanks for coming to x party" rather than cutting up the cake to give to the kids. I make large cupcakes, ice them with buttercream and out sprinkles or edible paper on the frosting. The cake boxes/nice sprinkles/edible paper you can get off eBay quite cheap-but that's my personal choice. It's just all done before the party then and we tend to have a cake at the party to sing happy birthday to then eat the cake after dinner as a family(singing hb again)
Music on in the background. Pass the parcel-on or off the castle (we do it on but depends on the room and if you want them to chill for ten minutes) a bag of haribo or similar between each layer of wrap.
A cellophane cone of black and yellow (batman) sweets, a balloon and a cupcake to take home as a goody bag.