thanks for the Reply @thedarkhorse. The cell phone is the best way to go for sure.
We have 4 cell phones in the house already and soon to be 5 - big house, big family - grandpa and grandma, daughter and 3 teenage grandchildren.
We needed one common shared phone number + 5 handsets to have phone access to that number anywhere in the house, so we went VOIP and love the savings and the service.
and grandma isn't a cell phone fan.
For sure with that many people in the house VOIP is a great option. If you just need to reach someone at the house and don't care who it works out perfect.