Your child is growing, and as long as he gets both physical and mental play, he will grow in strength and problem-solving ability. If he is improving in both areas, he is being challenged. If he loses interest in a toy, if it doesn’t keep his attention, then try another toy. Open-ended play is the best for problem-solving as it encourages creativity. Physically, you can observe, informally test him at home, and discuss his activity with the phys-ed teacher to make sure he is getting stronger and more agile. The inflatable slides are great because they support both physical and cognitive growth, especially if you let him help set up and invite friends.