Grizzly Grill on Princess at Division is the premier cougar bar in the city. Couple pool tables, small dance floor, two floors. Dress nicely though. No dress code (its a rustic cabin motif) and lots of guys will be wearing jeans, but smart casual is appropriate here and will set you apart from the rest. A suit would be over the top though.
You might also do well at The Merchant, on Princess just below Ontario (ie. near the water)
Brandees on Ontario, between Johnson and Clarence, is also a rockin' cougar bar. Your best bet, frankly, for boozy 30 somethings or above. Even the occasional 20 something will wander in.
Those three are your best bets. There are other bars, pubs and clubs in the same general area of lower Princess, Ontario.
I also recommend the Plaza Hotel (strip club), as it is like visiting the strip clubs of the 1980's. Old school, brother.
Make sure your hotel is right downtown. Don't stay at the Ambassador "Resort" or the Best Western, as they are not walking distance to the downtown entertainment area even though they are both on Princess. You want the Sheraton, Radisson, or Holiday Inn(in that order).