I've read that some ships have phones that you can use to keep in touch, but I'm fairly sure ours will not. As I will be travelling with the entire family, plus parents, etc., what is the best way to stay in touch without having to constantly set meeting times, etc.

Fair enough if we're in range of cell-phone networks, but any other ideas when cruising in the middle of the ocean? Are walkie talkies common at all?