Must have first aid items

Your best bet would be to take an organized first aid class before you embark on this endeavor. You will learn how to treat a variety of emergencies and will also learn about the items in the first aid kit and exactly how to use them. You also learn what you will find useful and what the essentials are and what you may not necessarily need ( like replacing the cheap plastic tweezers with a decent pair of metal ones) Most local red cross chapters hold regular classes.

I googled "what to put in a first aid kit" and found a lot of really good links.

I will agree with flare and say that taking a first aid class would be worth it. Otherwise research the internets for some good resources. One thing that I love having on hand for first aid kits is maxi pads. They absorb a lot and are great for stopping bleeding or dressing oozing wounds.

Anatomy of a First Aid Kit

http://www.emedicinehealth.com/first_aid_kits/article_em.htm

I always keep these things in my house, and in my vehicle. (consider it the boy scout/soldier in me to be a little over prepared, but better over than under)

You can customize your kit to accommodate your likely needs. with glass be prepared for lots of bleeding.

First Protect you, and other lay responders

CPR Shield

Gloves (latex free, non-sterile)

2 Cheap Clear safety glasses.

2 white dust masks

2-3 trash bags (make great aprons in a pinch or drop cloth to catch blood so you don't leave a trail out the door looking like someone got murdered)

1 small bottle of hand sanitizer.

Basics:

1 bottle hydrogen peroxide

Several pieces 4x4 gauze (sterile preferred)

Several non stick pads

Array of band-aids

butterfly closures

moleskin

alcohol pads

cotton swabs

Adhesive tape (surgical and duct)

sharpie marker

notepad and pen and pencil

2 Emergency Space blankets

3-4 bandannas (or triangular dressings)

Scissors/Shears

Forceps

Hemostat

Flashlight (mini mag light)

Medications

Diphenhydramine (Benadryl)

Asprin

Ibuprofen

Pepto bismol

Glucose Tablets

Triple Anitbiotic ointment

Bengay

Extras I have and recommend, but not necessary unless you a going to be a ways from medical care.

SAM splints (at least 2) see link bellow

http://www.youtube.com/watch?v=lPmVTKuSbio

Quick clot pads

Make sure you are trained to do first aid and work only within scope of practice.

OP, you would never want to find you did the wrong thing and have an injury that should have been treated promptly and correctly by EMS, ER, or urgent care clinic -- turn out to be disfiguring or even life threatening.

It's just not that simple, and you are asking questions that lead me to think you will try to treat injuries that are severe by yourselves.

I agree with the suggestions to take a class to get a better idea of what needs professional intervention and what you two can handle on your own.