Adam,
1. coffee in the morning, but you'd have to alert climbers to it, otherwise they may forget unless they are camping there.
2. Beers at the end of the day, patio area, to drink them at.
3. a grill with hamburgers at the end of the day works well too.
4. chalk, tape, sling, guidebooks, extra belay devices, maybe some extra harnesses should cover the "oh crap, I forgot the xxx" syndrome.
5. A big sign that says climber's welcome. That or something that says "climber's please be aware, wild Feral Rat on the loose."