I don't know if this is exactly what you're looking for, but one of the hotels I got a group rate at was University Inn - http://www.universityinnseattle.com/. They have shuttle service to downtown (Pacific Place, which is pretty far from your venue I think) - http://www.universityinnseattle.com/about-the-hotel/complimentary-shuttle/. My group rate was $130/night, and that was over Labor Day weekend. There is complimentary wifi and parking, which are usually additional expenses in the downtown hotels.
We've found that most hiltons have free shuttles that run until 10-10:30 at night within a 5 mi radius of the hotel. 5 miles should be just far enough to lose that downtown cost. Use google to seach for hiltons and use the Directions tool to check that its within 5 mi. Don't make any assumptions though, the best thing is to call places and ask about shuttle services. Most don't put that super handy info on their websites.. and calling usually will get you the info faster. :)
We liked University Inn, too, but liked Silver Cloud Inn even better. Our wedding was this past July, and we received a special event rate at Silver Cloud for $159, though a few people got even better deals. We used the U-District Silver Cloud, where there is free parking, free breakfast, free wi-fi, and also a free shuttle traveling within a three-mile radius.
There are also Silver Cloud Inns in the Capitol Hill, Lake Union, and Sodo neighborhoods, though the amenities are probably different, and the price likely varies, too.
Thank you for the suggestions. I'm checking on a bunch of hotels this week.
Click on each tool to see a sample.