A little more information would be useful. I would assume you are talking about going to Europe on a cruise since you are on a cruise forum. But you need to provide more information about WHERE in Europe you will b for us to be able to provide any info on phones and calling cards.
IF you are going on a cruise. You can be called on the ship if there is an emergency. Its not cheap, so I would only use that for emergencies. (You can call ship to shore also but the $$ applies there too). For basic contact (status updates etc) if the caregiver has access to a computer, you can rent time in the ship's internet cafe andkeep in touch with email or even instant messenger if the time zone changes don't mess with that.
Cell phone usage gets trickier depending on which countries you are going to and which cell provider you use and their international calling plans. But the cell phone would only work while you were in port anyway.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise, Magic 1/14
NCL Dream October 2006, RCCL Mariner OTS June 2007, Celebrity Silhouette 2013