First of all, Med/Surg IS a specialty.
Secondly, I echo the others, I would not leave my kids home at night by themselves, even with a responsible 18 yr old. This comes from a mom with 7 kids, and I understand how difficult it is to be a nurse with 12 hr shifts.
As for your age, mid 50's is still young. I think it is anyway. Maybe because I'm pushing 50, lol. I have no trouble keeping up on a med/surg floor and your med/surg skills will come in handy down the road when the time comes to leave, if you want.
In the meantime, embrace your position, your specialty, heck, become certified (yes there is a Med/surg only certification). It can only help you, if you do want to move laterally. (Notice how I said not 'up'?)
Believe me..btdt. (((hugs)))