Much like Moonstone, I'd rather she be saved for the sequel. Think about all that needs to be set up in the first film. We need to see Carol gain her powers, the death of Mahr-Vell, Carol get abducted, War Machine having some sort of role, some Kree villains like Yon-Rogg and Shatterax, etc.
Introducing all of Carol's Earthbound supporting cast is too much for one film. The origin story needs to be set in space.
Also, Kamala got her start by adoring Carol. How can Carol have a fanbase if she has yet to do anything heroic?
And I wouldn't put Sarah Day or Chewie in the first film either. I know it's Phase 3 but the last thing this film needs is to be overly cluttered and have a rushed pace.
The basic plot is going to be, "Thanos releases Terrigen mists over Earth at the end of Avengers 3: Part 1. Inhumans (human/Kree hybrids) awaken. Carol is one of those. Carol gets abducted by the Kree where she's experimented upon by Yon-Rogg and rescued by Mahr-Vell. Mahr-Vell dies and it's up to Carol to lead the Kree rebel forces. Carol does something to help the rebels and defeats Yon-Rogg. Carol hitches a ride back to Earth with the Guardians after the credits."
Does that leave a lot of room for Kamala Khan to be introduced? It's great that Carol has such a big supporting cast and more than one big memorable villain but that means that there's a lot of potential for sequels.