I agree with the toys like Legos, train sets, etc. Tactile things are excellent like play dough or moon sand (I myself could play in moon sand for an hour, as it's relaxing and such a neat texture....therapuetic really). Things like light bright, puzzles, etc. Things like playing in shaving cream, stamps, cutting magazines or those toy advertisement books, etc. I know you say he's not big on art, but sometimes when you just have the materials there for them to go at as they'd like, they really get into it. If you are down there with your four year old, preschool games like Chutes and Ladders, Hi Ho Cherrio, etc. that help with educational as well as turn taking and following rules. You could make sensory tables for your four year old to go to town in with little toys (like character guys, cars, toy bugs, etc)...can use water, pinto beans, dry rice, Kix or Cheerios cereal...we keep bins of each along with moon sand and play dough tools in those plastic shoe boxes to have on hand and do different ones each day or what not. Except the water of course is an empty bucket filled each time they play with it. Many of our toys are stored in plastic bins in the play room too allowing for the toys to be rotated easier so they are not playing with the same toys each day, and helping with cleanup too. For example, divided by Little people, trains, Rescue Heroes, play food, Duplos, treasure box which is all the carnival and happy meal toys, etc. etc. For play dates it is then easy to pull out a couple bins and they can go to town with those so there is plenty to do and cleanup isn't terrible. These things are fun now and really do help their development for later. My 3 year old is in OT for sensory sensitivity, and it's amazing how much these "good old fashioned toys" help them develop hand-writing skills, thought processing, etc. etc. Ideal to stay away from screen time and battery toys, leaning further toward manipulative, tactile things as those are the things that really encourage thought processing and motor development more. My 3 and 4.5 year old sons love all this stuff as there is always something different to do and they come up with new ideas on how to play with the materials there. Some are a little messy, but with setting up boundaries on where to play with it, how to play with it (gently, like not clapping hands with shaving cream on them to watch the shaving cream fly across the room, etc) trying to keep things in that area however you set the boundaries, etc., cleanup is really not bad compared to the time they play with it. 5 minutes cleaning up the moon sand or play dough that accidentilly fell on the table or floor is sure worth the 45-60 minutes they'll often play in it creating the different impressions, digging, and building. :) Best wishes...winter is tougher of course without so much outside time!! :)