I usually hang a couple of balloons
Then we usually do cupcakes or banana bread for lunch with a candle for anyone 18 mo + to blow out and we take a picture of it for the parents. Usually I put the bday pics in our next newsletter.
We also usually do a birthday craft. Either cut a birthday cake out of paper and let them paint/decorate it or let them paint a party hat or something like that.
I also buy a gift somewhere around $20 and send it home with the child at the end of day along with a card