Hi Penny1cent and welcome to cruise-chat,
first, congratulations on the first grandchild; being a grandparent is the greatest thing in the world.
Cell phones seem to be hit and miss; it all depends on who your carrier is and where you are--nothing dependable and nothing that works all the time; although I've heard of some that work worldwide.
e-mail works great, is dependable, and very expensive if you pay by the minute. But on most lines you can buy packages of time at a discount--still expensive, but with a grandchild coming, so what!
Wow!! A two week Panama Canal cruise and a grandchild all at the same time. Life is Good!