Screen time that takes energy is good - yoga or activity videos.
Once went for a walk with 3yo and FIL. Got to a playing field, FIL says 'I bet you can't run all the way round that' to DD. She does, happy as Larry. 'Amazing! But if course, you can't do it again, you're too tired.' Two jogging laps around a field while we watched, DD home having been exercised while we watched. This kind of trick can work!
Den building - blanket over the back of a chair, let DC take in blankets and toys, eat lunch in there etc. Or one of those kits where you connect sticks to make a den. Or a pop up IKEA play tent.
I think it's less exhausting if you basically plan the week as if you were a teacher, have a list of ideas up your sleeve. Dh could do this for you. So you don't have the stress of thinking of something in the moment.
I'd also be on the lookout for cheap secondhand toys to have a stash of things for a rainy day if you're desperate. Started this in lockdown and still so it as a security blanket! Eg big bundle of stuff for £5, play for a few weeks then sell on again.
If you're nauseous you might also find food prep hard - cd dh prepare packed lunches and snacks for ds so all you have to do is hand it over?
Sorry you're going through this, good luck!