I'm purposely ignoring the ammo issue, simply because I think it's been issued. The other things would depend on how long the mission was anticipated being, if they
are able to set up some sort of base, and if they have any kind of vehicles.
The general rule is that you are going to need two MRE's per day, as well as at least two canteens of water (more likely four given your mission parameters). Since it sounds like a search and rescue mission, they would probably set up a base camp, which would include a chow line, food for about a week, and at least three personnel dedicated to it (one cook, an armorer, and a communications specialist), as well as one officer in charge of the group and one for each group. There would also be one tent for command and food, as well as one tent for every four people (keep in mind that the officers and enlisted (which includes NCO's) would be separated).
Each merc would probably carry all of the usual equipment (which would include a radio, an excavation tool, a butt pack with a poncho, helmet, web belts (for first aid packs, insect repellent, flares, flashlights, and any additional tools), as well as possibly summer BDU's (lighter fabric than winter ones) and jungle boots (boots with canvas sides and reinforced soles; they would be comfortable than standard boots). I'd add night vision goggles (using light enhancement rather infra-red, simply because they would be navigating cool caves).
Arms and armor would depend on what was expected, especially given the temperatures capable in South America, even in the caves. Only if there was heavy action would flak jackets be used, and mostly because the weight would increase the personal body temp of the soldier, as well as decrease where they could go. Again, arms and ammo as been noted, but it would probably be limited to small arms (pistols and non-automatic weapons with no grenade launchers) due to the small spaces and pools that they would encounter (to avoid richochets and destabilizing the caves). Ammunition would be probably be limited to three or four magazines (base being close, as well as avoiding accidents).
If it helps...
FR