When DD was that age, 10-12 or 11-1 would have been perfect. By the afternoon we were usually hitting mardy and tired prime time.
2 hours is the sweet spot, 1 hour of them running about, bouncing and getting hyped up, 30 minutes to eat, sing happy birthday, blow out the candles on the cake, then you have 30 minutes for them to do a bit more bouncing while you bag up cake, clear the tables, get the party bags ready and they start filtering out.
We invited about 30ish kids for the village hall bouncy castle type parties, they don't all attend and you want enough to cause chaos, make it clear that parents will be expected to stay on the invite. We had one parent who breezed in handed over their 3 yr old and legged it. Not ideal as you really don't want to be responsible for a near strangers toddler when you're hectic. Give an RSVP by date on the invite and include your mobile number and a request for details of any allergies.
We never put on any kind of actual entertainment or structured games at that age, they have the attention span of gnats and are way too excited to focus on anything. A bouncy castle and a load of balloons to kick around was plenty. We did one party at a leisure centre which as well as a bouncy castle included a few softplay blocks, mats and the rubber/foam animals they can sit on and bounce, they were popular.
Food wise, we kept it traditional kids party but went with fully vegetarian so we didn't have to police the ham sandwiches to stop the wrong kid eating them.
- jam or cheese sandwiches
- platter of assorted biscuits, good ones in kids eyes - party rings, chocolate fingers, jam n creams, iced gems
- melon slices and blueberries
- cucumber rounds and halved cherry tomatoes
- packets of crisps (cheap big box of assorted flavours)
- platter of assorted cupcakes, mini rolls, mr Kipling style cakes
- breadsticks/cheese straws
They won't eat a lot they just want to go back to playing and no parent should expect a healthy nutritious meal at a kids party.
If you have the capability in the location then you can make the parts available for parents to make themselves a tea or coffee but for your own sanity do not set yourself up making the drinks for them, you wont have time. If the facilities don't allow it then some nicer flavoured water or soft drinks and biscuits/cakes are a nice touch.