Things we enjoyed last summer with my then 5 year old, yes to Jorvik, find the fossilized poo!
Couldn't get tickets to the HP golf but looked good fun, need to book in advance.
We did a HP morning on the shambles - went to potions class and then allowed to choose something from the HP shop, followed by the yummy food stalls in the market behind the shambles.
Really enjoyed the Van Gogh Immersive experience at St Mary's, my DD loved the VR at the end.
Again because we have a HP fan we went for a wander around Goathland to see Hogwarts station, have previously done the North Yorkshire railway which is fun. Combined that with a walk and play at Robins hood bay & visit to the little fossil shop there.
Enjoyed just walking around the walls, seeing the buskers etc.
If you're going in half term the Viking festival is on so will be loads going on I guess.