I think clowns would be an excellent choice! And yes you can mix them withing reason. I would stick to oscellaris to avoid any issues though. For instance dont get a maroon one and a regular nemo, the maroon are known to be super more aggressive than regular ones.
Might I suggest you not get a real expensive first fish? The picassos and snowflakes are awful pricey and if anything happened you would be out some serious cash. Just a thought.
The other fish mentioned would also be good, i had a royal gramma and loved her, she was very friendly.