.38 SPC: Nice! That has made my day!
I am a licensed EMT-IV (slightly watered down EMT-I), and work full time in the field. My take on it is this, if you're going hiking your main injuries will be sprains, fractures, and some strains. You ought to tailor your kit for that.
Don't leave home without: A cell or satellite phone or VHF/UHF radio with local emergency frequencies. Emergency medicine is mostly about keeping people alive long enough to get them to a higher level of care, not about "fixing" them. If you don't have a means to get help, you've already failed in your mission.
Drugs: Some ASA, ibuprofen, and motrin, imodium/pepto, neosporin, benadryl, cortisone cream. If you carry the med with you, make sure you know it inside and out (what to use it for, adult and ped dosing, side effects, route of administration, trade and generic name).
If dehydration is a big concern, keep an eye on your fellow hikers to make sure they drink lots of water. Easier to treat dehydration by preventing it than treating it once it happens!
If any of your fellow hikers take any meds on a regular basis or carry an epi-pen, make sure they pack them, and keep it with them. Remember you can assist patient with taking meds, you can't give it to them as a -B.
Dressings and Bandage: A dozen 4x4, enough klink wrap, a 4-5 rolls of ACE bandage. Bandaids of various sizes (nip small cuts at the bud from turning into bigger problems later on). Butterfly closures these can be used as temporary stitches. Slap 'em on, dress and bandage the wound, and its almost like stitches.
Splinting: 3-5 4" wide SAM splints will be enough for what you need. I'm hoping your crew is experienced, so they should not be breaking bones left and right. C-Collar: You got a SAM splint, don't you?
Other stuff: A compact CPR barrier device is good to have. 2 pairs of nitrile gloves. SHEARS, if you're an EMT you don't leave your home without your pair! Tape! Some Provodine and Alcohol wipes.
Nice to have: Some of those pressurized NS sprays for flushing wounds. Topical anesthetics, as Blake called them "feelgood sprays", nasal and oral airways, a c-collar, a LSB, O2, portable suction, and a paramedic and an entire ambulance.
Remember to strip your kit down to meet your likely injury cross-section.
Most of all, if you aren't trained or licensed to use it, DON'T BRING IT! You're flirting with loosing your license in the least, and being criminally liable in the worst. So don't! If its not in your scope to do needle decompression, administer narcs, or perform a crike, don't think you can get away with it just because you're off-duty. As far as my state law looks at it, if I am licensed, I am always "on duty" and must adhere to my protocols, standing orders, and guidelines.
Have fun, and be safe!