We're interested in the Best of Europe 14 day tour.
We are somewhat elderly and have medical issues that sometimes require immediate access to a toilet.
Would we be required to share a bathroom on any of the overnight stays on this trip?
If so, could we pay extra to have private accommodations?
This is a public forum frequented by volunteers. You should contact the Rick Steves office directly. See the "contact us" link at the bottom of the page. I would suggest you phone them and discuss your special requirements in detail.
Shared bathrooms are very rare nowadays. They are a relic from the past and the few hotels/B&B that still have them qualify only for one star and I doubt Rick Steves' tours use one star accommodations. But definitely check with them to make sure.
Even if your bathroom is ensuite, please be aware that it is likely to be small and the toilet is not likely to be a tall one, nor to have grab bars or anything similar. This is coming from a 70-year old with bad knees.
Related to that, there may not be many options for access to toilets while out and about. Be sure to read the trip Itinerary in detail for hints about that and ask the RS folks about it.
Also pay attention to the level of daily activity listed on the itinerary and take to heart the information in the Physical Demands section. The descriptions are accurate based on the one RS tour I've taken (Instanbul).
And don't forget you'll be spending a fair amount of time on the bus. The bus will have a tiny toilet, but the driver prefers you only use it in an emergency. You might consider a city tour instead of a bus tour. In a city tour you will never have to share a bathroom, and will spend limited time on public transportation.
If you do sign up for a tour, be sure to let the tour office and your guide know about your special needs. They will bend over backwards to accommodate you, or to suggest the best options.
By the way, many of the folks who travel on these tours are "somewhat elderly," especially on spring and fall tours, when school is in session. (Who me??!! Nope, not me! Welll...)
In 2016, that tour usually stays at Hotel Stechelberg, where a few rooms do share bathrooms. See recent discussion on this thread: https://community.ricksteves.com/travel-forum/tours/hotel-stechelberg. You can talk to the tour sales department about which departures are using that hotel and whether any are using a different hotel. In 2017, the plan is to use that hotel less often.