Our policy is similar to Willald's. Stay belted, but if it's deemed safe to move around, then they can do what they need to and then buckle up. All 12 seating positions in our motorhome came with seatbelts from the manufacturer, so it gives lots of seating options. Haven't put one on the commode, yet. LOL
If you need to add seatbelts, I can recommend
Gotbelts.com . They have a variety of styles, lengths, colors and mounting hardware options. I installed some across our bed so when we're travelling at night and the kids are sleeping in the back, they won't "roll off" should I have to brake hard. :)
~Rick