I have some mobility difficulties and whenever I want to book a place I ring up and check things like how many stairs, can they give me a ground floor room, do they have a lift etc ... it usually works fine and people are usually very helpful ... by law all places should have some "accessible" facilities so there's an increasing amount of suitable accommodation

so I would say to make sure you know exactly what sort of facilities your visitors need (don't make assumptions on what they need, check), look up places on the internet ... and get on the telephone ... by the way places like Travelodge, Holiday Inn etc are usually pretty good as most of them have ground floor rooms and the en suite is OK, and even if you're booking on the internet there is usually a space for special requests where you can put something like ground floor only