If you wait until 9-10, you could have 14k in LTCG, and be earning another 2k in gains every year. At that point, it could be very hard to bring down the capital gains.
If you do it now, you can keep up with it over time, and you can move the stocks to a broker who will charge no fees (you'd only need a handful of free trades/year) or to a vanguard mutual fund (which are free to buy/sell). Also, by doing it now, you could keep the LTCG low so that if she works as a teen she can easily move it to a Roth IRA.