When I first start potty training a child, I leave the potty in the hallway across from the bathroom so it's in sight at all times. It reminds me as well as the child!! I have never had an issue with any of the other children touching it or playing with it and we pass it multiple times a day. I do this for a week or two and then move it back into the bathroom.

I have a potty insert for the big toilet but very few of the kids like it so I don't use it often.

Pinterest has some good articles for potty training. Are you off at Christmas time at all? Maybe that week would be a good time to start if you are off or have lower dc numbers