Your kids are all grown and on their own. Your parents, hopefully, have planned for their old age. This is YOUR time. You've worked all your life, raising a family and all, time to take care of yourself now and enjoy a trip to Alaska. If family takes exception to that, then that's their problem. However, I bet they are happy for you if you do decide to go. None of us are getting any younger. If not now, when?
And if you don't take this opportunity to go now, someday you'll be sitting in a rocking chair regretting it. Think of it this way; you'll have stories to tell those grandchildren! Gramma, tell us a story. and you'll be able to tell them about the adventure you took to Alaska.