Hellobee Boards

I'm doing a bubble machine and water table for LOs birthday this weekend and hoping that's enough. I have play doh as a backup.

Bubbles
Maybe ribbon wands that they can wave around when dancing
We just went to a party where they decorated foam princess crowns(top hats for the boys) with the foam sticker.
Musical instruments
Art stuff-get a big roll of paper and tons of crayons

If you go with one entertainer what about getting a kids music teacher? We have a few around us that will do an entire 30-45 minute class and bring props for the kids like scarves and bells. By the time you do the class and food that might be all you need. You could get inexpensive instruments as favors and they could play with those too.

Another idea would be to set up a few stations, maybe a collage station where they could glue things down, a coloring station, a play dough spot etc. You could probably find an idea on Pinterest for a craft that could double as a favor too.

If you have enough stuff at home to make this work you could also set up your own indoor playground. Put out a tunnel, a little slide, blow up tons of balloons, put out a bowling set, make hopscotch with tape on the floor, make a balance beam with tape on the floor. You could lead the kids through it as a obstacle course with music and then let them free play. A parachute and freeze dance could round out the activities nicely.

I know you said you weren't too fussed on getting entertainers but my nieces just had entertainers for their parties (a magician for one and some people dressed as Frozen characters for another) and they were amazing...they did music/dancing/parachute games etc. with the kids and weren't particularly expensive. The best part was my SIL and family could enjoy the party without worrying about entertaining etc. themselves.