It would be simple for me. I would refuse to go to your restaurant because dealing with multiple systems is too much work for my feeble mind. And my wife tells me I'm better with math than the common person.

Your system is better. But it's special. Special is bad because I don't like having to do things X different ways for X different restaraunts. I would rather pay a little more and not have to remember the quarks of your restaurant. I am also just trained to tip so I will feel icky leaving your restaurant no matter if you are paying them a fair amount already.

So if you charge more money to include the tip I will still feel obliged to tip anyway and I will leave with the experience your restaurant is too expensive and not come back. In short I think you've done the right thing. Don't fight the mob, embrace it.