You've received great advice above. I'll just add three things:

1) Emphasize spaghetti's advice: "I'd not mention the grade skip to anyone-- at least not at the beginning because that's what they will have on their mind. The farther she gets from the grade skip, the more they will forget-- kids and adults alike."
IOW, beware of thinking "I know that we will get some special treatment since DD is a grade skipped child."

2) Middle school grades are retained in a longitudinal database along with a host of other information.

3) For 504 accommodations, "preferential seating" may be vague and have a whiff of elitism; "Seating near teacher" may be more precise and therefore easier to implement.