If you agree to contact your mom regularly to allay her fears, make sure you make it clear you won't be able to call her (or email or post) every night. Your cell phone bill may end up looking like that, but there'll be nights when no electronic contact is possible. Let her know ahead of time if you know there's a good possibility you'll be off the grid, but even then you might want to text her the next day as you ride through a town.Definitely do not promise more contact than you can or want to deliver. I made that mistake once and won't do it again. Do not promise to call every night.
(And to think a classmate of mine rode to Alaska after graduation, and kept in contact with his folks through five postcards over two months!)
That said I have found that often when signals are iffy a text message often goes through when a voice call will not. A text message is a great way to let folks back home know that all is well.