This post hits home for me. My parents were always involved with the kids even when we lived over 100 miles from each other. Often my dad would call and see if they could have the kids for the weekend. They even took them on a Disney Cruise and no parents were allowed. My in laws on the other hand lived 2 miles away and couldn't be bothered to see the grandkids. Both were retired, so that wasn't it. My daughter even asked grandma why she didn't buy her birthday presents two years in a row. No real good answer.
Well, last year my dad and my mother-in-law died 5 weeks apart. Both of my kids talk about grandpa and how much they miss him and spending time with him. DD even wrote an essay for school about how she cherishes his memory. Rarely do they mention grandma and I don't think either one of my kids cried at her funeral. She chose not to be involved with their lives.
IMHO hit the road, but don't forget to spend time with your grandkids. You don't realize how much they enjoy being with you even if it is just camping or playing board games. Priceless memories to them. Call or Skype they love to hear your voice and by all means don't forget their birthdays. It hurts them.