I agree with Rainier Flight for a first visit. I've taken lessons there and had some dinners and meetings, they seem very versatile. Call them and tell them what you need.
Galvin at Boeing Field has had rental cars on site but might costs more, so call them and compare. However, it is closer to Downtown Seattle, so it could be better if time is more important. Years ago I tied down over-night at Galvin. Outside tie-down was free if you buy their spendy gas.
If coming more often, perhaps you could get cheaper tie down and have a car delivered at an outlying field.
EAA 668340, chapter 326 & IAC chapter 67
RV-8 N89SE first flight 12/26/2013
Yak55M, and the wife has an RV-4
There is nothing
-absolute nothing-half so much worth doing as simply messing around with Aeroplanes
(with apologies to Ratty)