There is a nice Thai place I believe it's called Spicy Thai, NOT the thai place on St. Paul Street, this one is by the big bingo hall. It has charming decor and service and I've had very respectable meals there. In Port Dal there is a nice asian-y place, can't remember what it's called but it's in the main drag area and stands out because it's not a pub or crappy "north american" restaurant.
Some of my family thinks like this too
We had a very nice family dinner at coppolas. I had excellent carpaccio.
Spicy thai is nice, but good luck convincing a boring family.
Cafe amore on martindale could work.
My mother likes pow wow, although I havent been in years. Treadwell is great, but pricey, i dont know many friends/family in st.catharines that would want to eat there, as they wouldn't appreciate it. Some of them like to gorge at the all you eat.