I would say in this particular case that you could use the wheelchair icon, but maybe state in your cache description that the path is accessible but the cache itself might be hard to reach.
People's abilities are so different...what might be a fairly easy run across a lawn for a person using a motorized w/c might be a bit harder for a pusher. My husband is a quadripalegic, he can't bend over (although he's pretty good at falling over! LOL), he can't actually grab a cache, but a parapalegic would probably be able to handle that with little trouble.
I, for one, appreciate the efforts of anyone who takes the time to specify whether their caches are accessible or not. My husband and I are just starting out but we're having so much fun. And I want to thank one hider in particular in my area, Twinstars, who very often mentions whether his cache is accessible. And thanks to you, also!
Dawn