You mean you won't be working long in the field after you qualify?! We're going to be working until we're in our 60s at least...!
Seriously though, they don't even start thinking about age as a factor until you're at least a decade older than you are now. I have friends who were in their late 30s when they started Medicine and it didn't come up as an issue for them. You'll be fine.
As for my PS, I'd say something along the lines that while I am aware that I haven't followed the traditional path, I hope that the fact that I have chosen to undertake several years' study as an adult in order to be eligible to apply demonstrates my commitment and strong work ethic... something like that. Turn it into a positive.