We only found one play area at Woburn but that was with a 3YO on foot- it was pretty small.
Longleat has a huuuuuge forested one with loads of tunnels, slides etc, is amazing, plus many others.
Longleat is basically on two levels. The level you drive in at has carpark, plaza with shops, restaurants, pool, plenty of lodges up there. Also country club type place with crafts, nature activities, where all the Christmas stuff is.
Then you go down a huuuuge hill with the famed zig zag boardwalk. Pancake house at the top, tree top course and crazy golf towards the bottom. Huge lake with sports centre, spa, some shops/restaurants. Outdoor activity centre. No lodges down here. H
another huuuuge hill with zig zag boardwalk back up the other side to more lodges. These lodges are about a 30 min walk from the main plaza. So basically depends where you want to be. Any of the activities by the lake you are going to go down and have to come back up again, no matter where you stay. Stay by the plaza and no hills for swimming etc. If you’re over the back there is actually a bordwalk going round to the plaza without any need to go down to the lake and back up!
Everyone seems to walk/scoot more now. When I was a kid, I was probably 7/8 and with much encouragement was able to cycle up and down the big zig zags, getting stronger over the weekend.