Cheap, at home birthday party activities for 4x 6yr olds?

[tinysnickersaremyfavourite]

Aibu to ask for some ideas please?
My DS has his 6th birthday coming up and is determined he just wants to have his 3 closest friends over to our house.
But I'm a bit stumped what to do with them tbh. It has to be indoors as garden is a boggy mess.
Party games like musical chairs, pass the parcel etc would be a bit naff with just 4 kids.
They'll probably want to play a bit with DS toys but I need some sort of organised activity to keep them busy at least some of the time.
Has anyone done similar and got good ideas?

Hide small items eg buttons or beads around the house or one room. Prize for whoever finds most. A variation would be a treasure hunt with simple clues eg in a warm place (near radiator), where light comes in (window sill) etc. Picture lotto, giant snakes and ladders. My DSs and friends loved sewing cards at that age.

Decorate biscuits/cakes with icing & sprinkles.

Craft kits

Make your own pizzas

Lego building

Make some little dens, some cheap pick and mix sweeties, pop his favourite film on with some popcorn and fruit shoots.

All kids love pass the parcel, even if with just 4, you could pop an activity to do between the layers, like make an ice cream sundae at 6pm etc.

Treasure hunt (an easy version is to have a piece of paper telling the dc where the prize is, tear it into pieces, put each piece in a balloon and hide around the house, so the dc have to find the balloons, burst them and put the paper together and find the prize).
Obstacle course (you can to a lot with sofa cushions, can incorporate shooting a very gun or whatever toys you have).
I've done a version of musical statues with a small group where you shout out an animal when the music stops and give a prize to whoever does the best statue of that animal (works well with a bag of plastic medals).

Spy party. Set it up like an escape room, if their reading isn’t great you can do lots of picture clues/map clues. Mini assault course to get through - red yarn cross crossing a hallway for lasers &/or bells tied to it - get through without ringing the bell.
Spy pen/UV light pens are really cheap & fun.

Buy pizza bases and put lots of toppings in bowls so they can make their own. Same with desserts - ice cream with lots of toppings for them to choose from. there will probably be some waste and mess but That's an hour used up 😁

We did a dinosaur party at home with that number of kids.

Loads of brown and green balloons to play with, treasure hunt with (simple) clues, with each location having a plastic Easter egg with mini dinosaur toy in it. Probably not the weather for this, but stuff a small plastic dinosaur in a balloon, fill with water and freeze for 24 hrs. Cut off balloon, take a small hammer outside to smash the ice up to hatch the dino (I've had repeat requests for this by the kids). Pin the tail on the dinosaur.... we would have made dino masks if tye stuff had arrived in time.
I'd come up with a theme, and then base everything round that.
My "ugg craft, no way" child liked making wands and magic potions at his Harry Potter party. I dont think he'd have done it if it had been a random activity.