Gotham's is $$$$ if you can afford it. IMO for a more memorable experience go to a cheaper place but do more things
Take her to a nice small place in yaletown (or go to Glowbal which is always tasty as fuark... kobe meatball
),
or have a friend camp out @ cactus on the beach and get a good table for yourselves.
Or go to bridges on granville island (But go after 5 as they open up the top level and its got a very nice view)
Sandbar @ granville island is also good
here's what I think is a good idea:
Wake up late and go to an all day breakfast place.
Go bike the seawall on a tandem bike
Go to one of the aforementioned restaurants
Total cost = $100-$150 max and I'm including $30 miscellaneous cost for flowers/box of chocolates/etc.
Also, the day I've outlined is oozing in sappy shit, sappy shit is good stuff bro.
At gotham's you'd be spending $150 min. on both your meals with no drinks included in that price