They really dont need entertainment.
A group of 6 yr old basically run around like wild things entertaining each other. They have 30 second attention spans and arrive excited and in the mood to play.
We missed the 6 yr old party due to Covid but did a 5yr old and 7yr old with the 8yr old party planned for a couple of weeks from now.
What we find works well is:
Stick to 2 hours and if you can make it 11am to 1pm that way you have a natural lunch time.
Keep the food simple and vegetarian that way you don't have to worry about segregating food or making sure that the right plates are directed at the right children. I do jam sandwiches and cheese sandwiches, crisps, berry platter, veg stick platter, fun biscuits like jammy dodgers and party rings.
Stick age appropriate music on
Pick one activity for them, DD likes a bouncy castle which we did when she was 5 and we're doing for her 8th birthday too at her request.
Last year we had a garden party and it was all a bit last minute as had to wait on what restrictions would be in place so we blew up a billion balloons, got big boxes of garden chalks, bubbles and those tubes you swing round and they make an annoying siren like noise and just let them loose in the garden.
1hr playing, then call them all for food. 30 minutes for food and cake then let them loose for the last 30 minutes while you sort out clearing the table and getting the party bags ready. Parents will start arriving 5 minutes before the end.
One thing that was very well received last year but very messy was an ice cream sundae bar, we got a tub of neopolitan, one scoop per kid then they could help themselves to toppings which is where the mess came in. Bowls full of whipped cream, 3 types of sprinkles, 4 flavours of sauce, malteasers, m&ms, gummy worms..... it was a bit much and we were over compensating for Covid lack of socialisation and missed events.