You can eat anything you want, but no, steel cut oats are not included in the paleo diet. That said, I eat them sometimes, just make sure you soak them overnight first.
There's probably some value to eating quinoa if junk food is your alternative. But there is no need to eat it as far as I can tell though. Personally, I've yet to find quinoa processed to remove enough of the bran and/or saponin to not feel like a hot knife cutting through my gut while it is digesting.
I recommend that everyone try to go completely grain free for at least a month to see if they feel any better. And then add things back to see if they agree with your system.
Nope, oats are not paleo.
And there's no actual value you can get from quinoa that you can't get from other paleo foods. If what you like is the sensation of these foods, you can try the No-oat oatmeal http://www.paleoplan.com/2011/06-01/no-oat-oatmeal/ or paleo granola over here http://www.paleocupboard.com/granola.html