You're looking at the full attack rather than the single attacks.
Two unarmed strikes as part of a full round by using two-weapon fighting. It is still possible to get two sources for it, however! Take one like the monk's that can be delivered with any body part, say, kicks, and another source that does not involve other body parts than the fists.
You then have an unarmed strike for your fists and another for everything else.
As for the spell choice, I'll have to check the Cat Celebrant to see how it works. I think Elation would be the best option as a buff since it can affect the entire party and has both defensive and offensive applications to it. It doesn't last as long, however, so if you can spam spells then applying Heroism on everyone can be better in the long run although Heroism will probably get replaced replaced if the Cat Celebrant has access to the Good Hope spell later.
Edit: Oh, you can pick two. Nevermind then! Normally I'd say Summon Monster is better unless you have another source of summons but for our particular party we can probably manage without it. Heroism+Elation powerbuffing all the way! Only other one I'd recommend instead of Heroism is the almighty Alter Self. It offers more flexibility for your personal defense and in utility for puzzles, exploration/movement modes and so on.
