Good and interesting replies. Thanks.
I decided to go with one that opens at 5AM. This way I give myself an extra half and hour.
I may still do what beckoa suggests and walk back, since I figure if I get in at the facility 5AM opening I'll probably would have to wait for the shuttle to fill up before it moves out and by that time I would be at the terminal if I walked. I sort of remember that distance since I've been in KOA quite a few times so it shouldn't be time consuming walking.

again thanks.