We are a little older than you and our kids are in early 50's, we have two DGKs a boy 12 and a girl 13. We have been retired about 17 years and we have taken two long trips in that time. The first 10 or 11 years the DGKs were around we went to everything and were surrogates at a lot of events. Now that they are in middle school, we find that we aren't needed around as much. Two years ago we left on Sept 15 and returned the Tuesday before Thanksgiving. We had planned on doing something like that last year and this fall and also going again in early Feb for two or three months. Our plans have been interrupted by having a little bout with the cancer fairy. My radiation fatigue is lessening so late Jan or early Feb looks like a go.
So here is the big one, our DGKs are really pushing us to get out of Dodge. They have traveled with us since they were 4 and 5 and they really like it but know they have school and their social activities and their folks. We have talked with them about "fly/camp" trips with us. We leave in Jan Feb and they fly to us in Mar or April and camp, then back to school.
We raved about the East including Gettysburg, DC, Atlanta, Savanna. They both want to see those places with us. We don't like travel in the summer as the crowds can be a pain and campsites hard to come by so it's fall and spring for us.
I know this won't work for everyone but it is working for us. We do worry about our eldest DD as she has cancer too. She is in controlled remission most of the time but every year or so she is back on chemo. She knows that should things really go South, we will be on a flight home immediately. In the meantime, she is a hard working marine biologist and works some weird hours sometimes and has a husband that wants her home with him as much as possible.
Our entire family wants us to use our MoHo and see the country. We keep in touch by email, text messages and this winter we'll start using Skype. All our adopted GKs and their parents and grandparents around the world are using it and have asked when we will start.
You will miss them, but including them with fly/camp, Skype, text messages and letters, emails and phone calls takes the edge off missing them. If you find out it isn't for you, short trips and holidays are fun too.
Good luck and have fun.