I can tell you right off that I know nothing about having an older bitch with a litter, and that it is one of those personal decisions you have to make yourself.
What I CAN tell you is that I wish my JRT bitch had at least one litter. She died April 13, at 16 1/2, with no offspring, and she was a really great dog. If I could hop in a time machine I would do it differently.
I'd heed the advice about the cost of a C section though, maybe your vet does it cheaper, or you could call around in advance for prices, in case. If she's a great bitch, if even only to you, you may want to risk