Are the children coming for 3 hrs Forestfly? That's quite a long time. Some quieter/longer activities which have worked for us in the past are:
A creative/food activity ... we had DIY fruit/ice cream sundaes one year ... provided loads of chopped fruit, sprinkles, squirty cream, and some ice cream. The kids spent AGES on them and really enjoyed them.
Or decorating biscuits.
You can also have a "colouring competition" ... set out some pictures, or masks, or something at the beginning for when the children arrive. They can have a bit of time for colouring then. But they can continue doing it during the party ... when they've been knocked out of a game, or if they don't want to play, or when they've finished their food early, or whatever.
Sitting listening to a story - maybe get them to join in with some actions or making animal noises, or something.
Also just singing together, or doing singing games ... like The Farmer's in his den, and In and our the dusty bluebells and similar tends to go down very well. Ask your ds which of these songs they sing at school in PE/music to see which ones they know.
Oh, also parachute games ... If you can beg, borrow or steal a parachute from school if you're on good terms with them, or a local Cubs/Beaver group, or youth group or whatever. They are pretty easy and tend to go down well.
How good friends are your friends? Can you make a list of games, and ask them to take responsibility for 'leading' a couple each, to give you a break?
In order to stop the kids getting too manic, make sure you alternate busy games with quiet ones. Once we brought mats/cushions for the children to sit in a circle whenever we were talking with them.
Also: Get them to sit down and listen whilst you carefully and slowly explain each game. Some of them may not be familiar with party games, and it also helps them to calm down a bit.