Your best bet is to just give everybody a calling card and have them call into home or whatever and leave a message.

It would be better if you had cell phones that could roam in the places you were visiting, but given that is not an option, the message drop may be the best choice.

If you have devices you can skype on or whatever, and you have wifi you can set up something that way, but it depends on the timing and where you are and what you are carrying.