I don't have any particular printer suggestions, but...
If you know the Epson printer will work for your folks, buy it. It's a nice way of showing your support for a product that actually works with Linux.
linuxprinting.org is a great resource. You have to take "works perfectly" with a grain of salt, by they are helpful.
cups.org is another great resource.
Basically any Linux forum is a good resource. Ask people what they are using, see if they had any problems and go from there. Your linux flavor's website is a valuable tool for you. Maybe the Epson printer works great with your Linux but it will not with your parents.
Turboprint is an option. ESP Print Pro is another. These are commercial products, whether you need them or not is up to you. For plug and go, I'd say yes. But, if you're willing to tinker, maybe sweat a little, don't go commercial. I know my friend likes to twick his printer and system. This is fun for him.