For the first day, swimming or an adventure playground in a park/woodland. Find somewhere with a good cafe or take a picnic. If there are any indoor swimming-pools near you with slides or splash areas for younger children, those are great - my DC will fall asleep on the sofa after a day out at our local one.
Then back to yours for baking, painting or similar, depending on what you have in the house. My 5yo loves baking but it does make a mess. We tend to get those cupcake kits - the Spectacular Science ones are quite fun, or you can get dinosaur or Paw Patrol ones depending on what he's into. Cutting and sticking is also a hit with that age group - you just need a glue stick, scissors, a piece of paper or card and whatever scraps of paper you have around the house.
Pizza, film (recommend Paw Patrol movie, Planes or something NOT scary) and popcorn for the evening. Put child in pyjamas before the movie starts in case he falls asleep during it, so he can easily be transferred to bed.
For the next day, I'd recommend soft play. Hopefully there will be other children there for him to play with, so you don't have to go in the frame yourself 😁!