I need to plan an enemy party's camp, but they don't have an arcane caster.

It's a pretty high level group - an 18th level cleric, 2 15th level monks, a noble Efreeti (and his Cauchemar mount), a Cornugon, and a Kenku Ranger 2/Rogue5/Assassin 10.

I try to limit myself to the Spell Compendium and the PHB for spells, as I find dipping too many sources just causes power creep - though for flavourful spells I'll go outside of these.

The Cleric has Magic and Knowledge as domains.

So, how would this group make camp when awaiting the return of one of their members, at the base of a mountain? They have the choice of going into forested area, staying in the open on a hill, or even of using a cave or something. They know that there is an opposing party in the area, but they dispatched a pair of demons to harrass them in the night (a Nalfeshnee and a Marilith), and plan to hit the PC party the next morning. They have to stay roughly put, since they are waiting for another member to rejoin them.

What spells would a cleric use to guard a camp, and what UMD-able stuff that is fairly low cost would they typically use (unlimited wand of alarm, etc?)? Would they have magic bedrolls, and thus need little sleep? (I assume so).

Thanks for any input/spell selection suggestions. I assume they wouldn't want to use a huge amount of their daily spell allotment on camping, nor would they typically be using effects like forbiddance, as even higher level parties don't blow 1,500gp per night when camping.