Personally, I'd go eat wherever I want to. I highly doubt that even in the off chance your ex-T ran into you at that restaurant that she'd jump to stalking. You are there with another person as public restaurant.

The ONLY reason to not go is for your OWN level of comfort. If you feel you will be nervous, anxious, etc. because you won't get this out of your mind the whole time, then yes, suggest a different place. You don't have to explain why. Just say, "Changed my mind. Can we meet at _____?" and go there.