Play games with him - my DC loved games nights
Have movie nights. Make sure he's seen all the classics like Shrek, Toy Story, Studio Ghibli films, Incredibles, Up, Bee Movie etc.
Get outdoors and active with him. I used to love cycling in the woods with DC. They definitely lost interest and preferred going with friends as they got older. Same with going swimming (outdoor pools, wild swimming as well as leisure pools with waves etc.)
Usual outdoor stuff: build a dam over a river, build a den, climb a tree, camp in the garden, build a massive sandcastle and decorate it, build a campfire and toast smores or marshmallows over it.
Visit Legoland, Science Museum, Maritime and Natural History museums.
Panto & circus
Read with him at night. Harry Potter, Alex Rider, Young Bond, classics like The Silver Sword.