Welcome to Smogon! Take a moment to read the Introduction to Smogon for a run-down on everything Smogon, and make sure you take some time to read the global rules.
Oh, right... Hmm... That really is a hard decision for Arceus, but I think I'd do Adamant. You're choice though. :P As for Shaymin, it gets Earth Power, but I'd still catch it with that spread.