Given your needs & budget, your best bet would be the Lord Amherst (www.lordamherst.com), at 5000 Main Street -- right across from the test site. It seems to have all the things you're looking for. Not sure the continental breakfast is included in the price, but I think it is. They also have an on-site restaurant for lunch and dinner (Sonoma Grille); I just had lunch there the other day, and it was out of this world (though a tad expensive).
The Lord Amherst is just blocks away from the center of the Village of Williamsville, a lovely, walkable area with many shops & restaurants. What kinds of food do you like?
You can also take a short drive to Niagara Falls Blvd. to shop at the Boulevard Mall, T.J. Maxx, DSW Shoe Warehouse, Target, etc.