It really irritates me when guests walk through our bedroom to use our en-suite 'because someone else is in the other bathroom' or because it has a better shower. They don't do it when we're in bed but I prefer to keep our bedroom and en-suite out of bounds even in daytime.
The family bathroom is right next to guest-room, although the shower over bath is set low on wall, so if they want to shower they have to crouch or sit in the bath (walls are part-tiled). However I've used it myself many times and its not difficult to use. DH thinks we should also offer guests use of walk-in shower in en-suite as well, but unless they have mobility problems I don't see why they can't use family bathroom! In my experience once they use en-suite shower they keep popping in and out to use loo/brush their teeth/get changed etc, which I find intrusive.
AIBU to not offer en-suite, and to politely ask them to use other bathroom?