I've been with a group of year 1 children. It was nice... Not amazing... It depends if they're into looking at things rather than doing IYSWIM. If you're already there though, you might as well visit. Definately go to Brockhole visitor centre though, there's a massive adventure playground, horse riding, you can go down to the lake, have a picnic/ lunch in the cafe. Ds (nearly 4) loves it there.