We pretty much took our kids anywhere we went as toddlers so yes, they were use to eating at nice places. A few tips that help.
-Go a bit earlier. more families, less couples looking for quite and romance, kids less tired.
-Let the waiter know you are on toddler time. With DH only, I like a long slow meal....kids?,,,,,, nope. Be ready to order, consider skipping apps etc.
-Make sure the kids are hungry, but not starving. Have a few crackers along or ask for something.
-Get a booster but don't use it till the food come. You only have so much containment time.
-Order then walk. Take your toddler outside in the lobby or just outside to let them walk a few minutes while waiting for food, or between courses.=
-Take entertainment that does not disturb others. Stickers, small toys etc. I am not opposed to handing a toddler a phone or i pad with NO volume to allow the adults dessert and a glass of wine. Others disagree.
-Make restaurant rules. At two they were simple, stay on your bottom, use your fork or spoon and use inside voices.
-Remove immediately if necessary. Did not have to do this many time, but its important. Find an out of the way place and give a time out or whatever you use.
It really is worth the trouble to train the kids to enjoy and appreciate nicer places. DS now 8 was about three when we stopped for a rare fast food lunch once and he wanted to know if he could order calamari for his appetizer.