I think some kids like colouring books/mosaic/decorating kits etc, while others prefer doing their own thing from scratch?
In our house (6yo dd and 9yo ds), arts and crafts kits intended for specific projects tend to be ignored/forgotten, while plain paper and new markers/stickers/glitter pens/scissors are happily received and used all the time.
At 4yo, either of them would have been delighted with a bunch of craft paper in different colours and sizes, perhaps scotch tape and a pair of scissors, glitter pens, glitter glue, lots of sparkly stickers, and nice new markers.