Just because I've been there and done it doesn't mean that you can. You know your limitations, I don't, so if you go there it is at your own risk. By mentioning the place I'm not suggesting that you go there.
Moors Valley Country Park & Forest, Horton Road, Ashley Heath, Dorset, BH24 2ET
Moors Valley Country Park, near Ringwood in Hampshire and Bournemouth in Dorset has gone a long way to make it accessible either using one of their own all-terrain mobility scooters, Trampers, provided by Countryside Mobility, or one's own. Standard mobility scooters, and some powered wheelchairs could maybe manage the main paths, and the visitor centre. I've used their Trampers twice, which were good, but I'll probably take my own next time.