Hiya,
Remember, 1" of fish for every 5 gallon's, so you could probably get away with 5 inches of fish. Nano's fill up with waste a lot faster, so you're going to have to really stay on top of water quality if you try to over crowd it.
I'd go with pair of clowns and either a firefish or a cardinal. Definately nix the manderian, I lost my scooter, same family of fish, just recently due to not having the correct dietary needs.
I believe you'll need MH for the claim, so you may want to reconsider it. Anenomies after six months of set up, they need good water quality and lighting too.
As for a cleaner shrimp, my peppermint is a hoot. He comes to the front of the glass and watches me and is always one of the first to come out when I feed.
Meadbhb