I don't have kids, so I'm not the most qualified person to write on this topic, but I'm totally enamored with these subscription activities boxes for kids.
Kiwi Crates are designed around fun themes and filled with all of the materials and inspiration
for hands-on projects: arts & crafts, science activities, imaginative play, and more.
BabbaBox is a monthly subscription box that is delivered to your home with all the physical materials plus know-how content to really engage with your kids. There are four major components in each monthly box: creative projects, a theme-based exploration product, curated books, and interactive learning downloads.
Have you tried either of these subscriptions? Or something similar?
(Photos from Kiwi Crates and BabbaBox)