Oof this is a tough one. Before you mentioned the seasonal aspect, i was going to mention the pea patch library readings in the summer on Delridge.
When my kiddo was closer to your kiddo’s age, I searched for swim lessons because that is an important safety skill and tires them out. I found a woman giving affordable lessons at the Evergreen pool in Burien.
We usually also shared a meal once a week with another parent of a young child because it was easier to parent two kids together than one alone. We’d alternate houses and make pasta usually.
The gym that ended up working for that stage was the Y (in the junction). My kid LOVES the kid zone and the hours are consistent. He’s still excited to go.