There are two routes that are basically the same amount of drive time (only about a 20 mile difference in the two routes), and both are very common to take from PDX to Sunriver. One is to take I-84 to 26 to 97, and along that route there is the Kah-Nee-Ta Resort in Warm Springs. The other route is to take I-5 south and at Salem cut over onto highway 20. Two places along that general route to stay would be the Oregon Garden Resort in Silverton (east of Salem basically) or somewhere in Sisters, such as the Five Pine Lodge.
Another option is about 30 miles longer, but also very nice. That is to head our on 84 east and stay in/around Hood River and then take 35 down to 26 and then to 97.
It just depends on what you are looking to do for that night. It is normally about 3 1/2 hours from PDX to Sunriver, so not a long drive at all.
What time of year is this? Is there anything you are thinking of doing along the way?