I take my kids out to eat by myself quite a lot - the biggest issue for us is not the restroom itself (usually), but having to leave our table unattended while we are in the restroom. Even if we tell the waiter, more than once we’ve had our table cleared because they thought we had gone. We solve this problem (baring an emergency, of course) by visiting the restroom immediately before being seated - bonus is our hands get washed directly before the meal - and not going anywhere where the meal is likely to take more than an hour. Really, meal-time bathroom issues are almost a non-issue for us.