When we started full-timing 17 years ago we didn't have a cell phone or computer so we had to do it a little differently. We called on the public phone (yes, standing in one of those phone booths that are now in museums), mailed them small trinkets and constant post cards of where we were, mailed them photos of where we were, including some of ourselves. Nowdays with cell, Skype, computers, Facebook, etc. things are a lot easier.
We took them with us on trips and stayed big chunks of time at a campground near their homes on long vacations. We were always there on Christmas, birthdays - when they were younger.
It's all very doable and a lot easier these days. They honestly don't know of any other lifestyle for us and they've always had a very good relationship with us. Now the youngest is 12 and they're all into their own sports and activities but we all still see each other as much as possible.
Remember the phrase...quality rather than quanity. It works....