Just been to the website, plan looks great!
Embarrassed to confess, that because it was a packaged tour, we
were pretty much led around, so I don't have precise
recommendations with names and addresses for you 
What I think you die die must try and are probably already in your
itinerary, are:
Ice cream. Milk, lavendar and melon flavour. Someone told me cherry
blossom flavour tastes like cough syrup
Hot spring , indoors & outdoors. Don't soak excessively long
please, will get giddy LOL. And communal baths
I'm not sure if they still have it in July, but in the evenings,
there are fireworks over Lake Toya. So if you have a room
overlooking the lake, remember to stay in after dinner to watch the
fireworks 
V romantic neh 
Ramen . Actually I find they are close to what we have here.
Seafood - urchin, crab, scallop
Fruits - strawberries , melon, etc
If your girl is a shopper, Sapporo has a Burberry Blue Label shop,
it's in a dept store near the TV Tower. Tourist == tax-free.
There is also a factory outlet mall at Chitose called Rera - Coach
store got discount! http://www.outlet-rera.com/
Posh pastry / cake shops - can go in try sample. The cakes,
chocolates are very good.
