There are two close-by hotels to consider.
We have a discounted room block at the Double Tree Hotel in Westminster at 8773 Yates Dr, Westminster, CO 80031. It is just 7 miles away and they have a free shuttle to and from the Mart. This is a newly renovated hotel and includes breakfast, shuttle service, full pool and exercise room as well as wifi. Reservation link Here.
Another option is the Comfort Inn, attached to the Denver Mart. They never responded to my requests for a group block, but they should be reasonably priced and are certainly close by!
Also, for more information during your stay, check out the Denver Convention and Visitors Bureau here.