We are a Senior couple taking a road trip starting in NYC to Buffalo, Niagra Falls, Niagra on the Lake and Toronto in August.
I need your help in planning a perfect day of celebration for my wife while in Toronto. She is a vegetarian, photographer ( especially street art), loves live music venues, museums, going on walks, exploring neighborhoods, enjoys a nice glass of wine.

I would like your help me in planning a " perfect" day of celebration for a very special lady!

Thanks!

I see you haven’t yet had other input from Fodorites who would be more knowledgeable to respond so I’ll often some suggestions:
1- Street art: Graffiti alley off Queen street west (google it for lots of articles with info)
2- So many great neighbourhoods:Queen street west; Kensington market; Chinatown; Danforth area; the beach area near Queen St east & its lakefront boardwalk; Harbourfront area; Toronto islands- I’m sure I’m forgetting something (oh right, not my favourite but the Distillery district)
3-vegetarian food: most places have choices for vegetarians (a little less for vegans). A great restaurant for visitors to the city/ views/ delicious food is Canoe however their menu tends to be based on meat/ fish proteins however I have dined there with a vegetarian and they did offer a choice (not sure about your budget)
4- I’m not sure you asked about hotel recs but I had a “staycation” at the Delta in a corner room with a large soaker tub that faced the lake/CN tower- I was pretty happy! (again the budget would be a factor here)
5- Museums- there are many small museums that may be of interest (Gardiner if interested in ceramic; Bata shoe museum) however the largest is the Royal Ontario Museum.

A birthday day plan could go something like:
Breakfast coffee and delicious croissant at Le Gourmand on Spadina just south of Queen (right where Graffiti alley starts); walk along the alley (although a photographer might prefer to be there later in the day for better light, there may be fewer people earlier in the day);
From here Chinatown/Kensington market/ UOf T/ Queen’s park to ROM would be a longish but good walk if a nice day and you are walkers otherwise it’s possible to use uber or hail a cab; If looking for lunch before/near the museum there are several great choices in Yorkville (one well reviewed vegan restaurant that I personally haven’t tried but is near the ROM is Planta).
Have fun planning what I hope turns out to be a “perfect” day!

Also, I would suggest putting your dates into Ticketmaster and Toronto.ca for Events and shows t0 see what events are happening. I see a concert for Santana and Earth Wind and Fire in August, as well as a Caribbean Food and Music Festival. Also consider the Bata Shoe Museum for a unique museum; their collection covers footwear from pre-history to Elton John's platforms.

Took my wife to Toronto a few years back for her birthday, got a good deal at the Fairmont Royal York - great historic hotel. There are a number of other nice hotels nearby. Ideal location a few blocks from the waterfront, St. Lawrence Market, Distillery Historic District, CN Tower, Art Gallery of Ontario, and Fashion District. King Street area in the fashion district had a number of restaurants. While a bit touristy I recommend making a lunch reservation at the CN Tower, it includes a free ride up and you bypass the usual lines.