Hi - Question for those who might know how busy the Admirals Lounges are at LAX...

I was thinking to pre-purchase 2 lounge passes for a flight on Wednesday, Oct 22 of this year. We arrive into LAX on economy award tickets from SFO on Alaska Airlines (likely Terminal 6?) at 3:42pm and will depart on Qantas from Terminal B at 10:10pm for the long hall to Sydney, Australia, and a further 3-hour connection before a flight to Adelaide. It's brutal to start such a long flight with a 6.5 hour layover. We booked the award flight months ago and the times have changed several times for the worse. I tried calling to get the award tickets changed but that did not work out.

Questions:
1) If I book the day lounge passes in advance, is it likely we will have no issues with getting in because the lounge is full? If they turned us away, I assume we would get our money back?
2) Any tips about which Admirals Club to use?

We don't have any other way to access lounges so would appreciate your help. I have also considered booking an airport hotel but my travel companion prefers a lounge. Any tips at all would be appreciated! Thanks.