There are several companies that provide rental gear such as rafts, satellite phones, expedition water filters and provide food packs. While these can make organizing your trip much easier it is still your responsibility to know what they are providing and how to use it.
Rental rafts can help if your group has rafts that are smaller and you need bigger raft(s) either for safety or carrying gear. But you will need to have people that are comfortable rowing the rental rafts that may be different than what they have rowed in the past. Rental rafts may also be rigged very differently. It is difficult enough to row the big rapids in the Grand Canyon but doing it in a strange boat and rigging to prepare for flips in a reasonable time can add to the difficulty. The rental companies usually provide orientation both before the trip and at Lee's Ferry that can ease the transition to using their rafts. They also usually provide boat maps and blank boat maps for you to record where everything is stored. It is your responsibility to review all the rigging and to be familiar with it before your group launches.
Many groups decide to have an outfitter provide a food pack for their trip. This can greatly simplify preparation for a trip but it does not absolve you of the responsibility to know what they are providing. The outfitters generally do not have food preparation licenses so they are basically going to the grocery store for you. All meals will be cooked from scratch which will take time on the river. Even though someone else is preparing the food pack you will still need to check on Food Preferences. Ask a lot of questions about what they will be supplying. Lee's Ferry is the wrong place to find out there is a problem with the food pack. Even though you may not be doing The Food Pack you should review that section to get an idea about what questions you should be asking.
Outfitters will generally provide a lot of food so that there is no risk of running out. Too much food is almost as bad as not enough when you are lugging a lot of food every day and have no place for the food that is not eaten. It is probably a better idea not to have way more food than you can eat at every meal and instead to carry emergency food in case you run out or need food for extra days. Remember, it is your responsibility to make sure the outfitter is supplying the appropriate amount and type of food. You should also have detailed maps of every raft showing what is stored on each boat and where it is stored. Do not wait until you have seven rafts moored way off South Canyon ready for the water to drop overnight and have to wade out and climb onto every boat trying to find something.