I have always loved the AGO - I have been a member here (off and on) since I was 12. It helped that I lived across the street from the gallery for a couple of years during senior public school.
There is truly something for everyone at the AGO - from kids programs, to special member events, world class painting exhibits, African artifacts, photography and a decent size art shop. Everything the AGO does is absolutely top shelf - inspiring and stimulating for the mind and soul.
In terms of eats, there are three options - Frank (a full service restaurant), the Ridley members' lounge (soups, high tea, etc) and a cafeteria (sandwiches, coffee, etc).
Yelp Tip - if you have an Albright-Knox Associate membership you have reciprocal privileges at the AGO for general admission! Special exhibits are an additional charge, but still an amazing value (usually $10 Cdn).
Definitely put the AGO on your Toronto must-do list, you will not be disappointed.