I looked into this and came up short. Every device I own or looked into purchasing can only do one account at a time. To use a second you have to log out of the first. Our current work around is anyone wants to listen to Pandora, they just stream it from their own phone.
I did come across that Rokus and WD TVs support multiple accounts but haven't tried it out. The downside to that is it needs to be hooked up to a display to see what you're doing.