Multiple Learners, 2 story home

I have a 4 year old Springer who understands the concepts of the buttons. I bought larger buttons from Amazon while waiting for the FluentPet buttonsΒ  to arrive from backorder. He was using them to communicate (I got as far as Outside and Play), but the buttons were pretty huge for my 2-3 year old (he's a rescue, we don't really know how old he is) JRT 12 lb mix. It ended up that the Springer would press Outside for the JRT mix. The smaller dog was the one that would really want to go outside.Β 

My questions are:

1.Β  How do I handle multiple learners? I'm hoping with the FluentPet buttons the JRT mix will join in as the buttons are easier for him to push.

2. Do I only reward with praise (not treats) and a reaction (Outside = opening the patio door), or if they press it and no sound comes out, should I still praise/react?

3.Β  I live in a two story home, so can I keep the Outside, Play and All Done larger buttons on the first floor, and then start with an Open Door button on the second floor in my office? I've moved my office upstairs so I'm not around the original buttons much anymore. Or should I move the original buttons upstairs?

Thanks for your answers!