Toronto Harbourfront hosts various music and culture festivals on weekends in the summer and the World Cafe there offers a changing variety of inexpensive multicultural foods. There is also an outdoor craft market, several patios and a number of sightseeing boat tours (within walking distance of the St. Lawrence Market, the Island Ferry and the CN Tower).

The St. Lawrence Market offers lots of food and snack possibilities (although your husband is vegetarian, you might be interested in checking out Carousel Bakery for their famous and iconic Canadian Bacon on a Bun sandwich). I see that you are visiting Saturday to Tuesday so you should note that the Market is closed Sundays (except for an antique market) and Mondays. Saturdays are liveliest.

Your say you like beer: The Toronto Festival of Beer is on that weekend. I have not attended but information at their website: http://www.beerfestival.ca/about-festival

ROM is a great museum. It's near the upscale Yorkville neighbourhood - restaurants are generally expensive but there are cafes and patios for a drink while people-watching, and window shopping (and potential celebrity-spotting) are popular and can be fun.

St Lawrence Market is a wonderful place for vegetarians and just an all around great place to browse and people watch. We spent 5 weeks in Toronto last fall and I never tired of the St Lawrence Market; we went there countless times. I loved the eggplant Parmesan sandwich served on the first floor close to a souvenir concession. I can't remember the exact name, but something to do with mustaches. The sandwich is huge and my husband I split it. We always determined to try something else, but always ended up with the eggplant sandwich since it was so good. I'm a vegetarian and had no problem eating in Toronto. The food is wonderful.

Another vote for St. Lawrence Market.
I'm not a fan of Dufflets, I think it's more hype than taste, but that's only my opinion.

The Distillery District (where Mill Street is located) is interesting to wander around. http://www.thedistillerydistrict.com/index.php I like Pure Spirits Oyster House for lunch or dinner.

Also Soma Chocolate
http://www.somachocolate.com/

The Senator Diner on Victoria near St. Mikes Hospital (Yonge/Dundas Sq.) is great for breakfast http://www.thesenator.com/

Thanks for the advice. We will add St. Lawrence Market, Harbourfront, and Distillery District/ Soma Chocolate. What are the best bakeries? Are there any good Italian bakeries in Little Italy? I love Boston's and San Fran's Little Italy. Is it at the level?

Check NOW Magazine for festivals that weekend. You can pick it up free on just about any corner or google it.

If you're in the Spadina and Bloor area (known as the Annex), there's a very popular veg restaurant called Fresh. Have dinner and then walk west along Bloor to Bathurst -- nice funky shops, restaurants, lots of yogourt/topping places. I prefer Menchies. It's a nice walk in the university area.