(I'm in the process now, so this is just advice I've heard other people give - my first possibly combative meeting is tomorrow, people so far have been good)
First thing, which it sounds like you've done, is to research exactly what the rules are for your district.
Then, I read up on the language to use with teachers, like avoiding "bored" and making sure you say "appropriate". I'm also using phrases/concepts like "learning how to learn" "good study habits" "rising to a challenge instead of avoiding it". They're principles that everyone can agree are desirable to learn at school.
I also try to keep in mind things like making sure I hear what the person needs to tell me and acknowledge it. The classroom teacher needed me to acknowledge what her job involves before I could go and ask her to do more work accommodating my child.
Having said that, full grade acceleration is a pretty big step. Do you have to go in asking for it? Why not just say "We wanted this meeting so we hear your ideas for the best/easiest way to give her appropriate material". And let them think it's their idea.
I would look into testing, and using the Iowa acceleration scale to figure out if it's really a good idea.
