Sounds like some nice parks.
27% shouldn't be a problem unless you have a loose surface and no 4wd. The state maintaned gravel road to my property has several sections that steep and I go up and down it fine towing. My daughter and son in law have taken their 38 ft class A up and down it as well. Just take it slow and steady. There are also many forest service roads with grades like that. We have small trailers meant to enjoy those kind of destinations.
The narrow roadway is more of a problem, possibly. Vehicles heading up have the right of way but vehicles towing have the right of way both up and down so unless you're going down and just happen to meet another trailer going up you should be fine. To avoid that particular situation you can leave early in the morning when headed out.