Personally I think adding Montessori to your current Reggio/Waldorf blend makes it less of a niche. I would think focusing on one and possibly 2 means you would appeal to the families that are seeking that but once you starts trying to advertise that you do all 3 you seem like you are just throwing out key words to draw people in and aren't actually focused on any of them. If i am looking for a Montessori daycare I am not looking at Waldorf/Reggio/Montessori daycares.

I also wouldn't suggest changing your current way of doing things (if it has been so successful) at the same time as a big move. Stick with what you know and specialize in and keep the added stress down.