Russell Simmons put his daughters Ming Lee, 12, and Aoki Lee, 9, on a (generous) budget for some back-to-school shopping at J.Crew in East Hampton last weekend. Simmons was spotted in the store with his girls Saturday — but as they eyed racks of new fall clothes, Simmons was overheard telling them they each could spend no more than $750 on the store’s preppy goods. The girls then went ahead and grabbed items as their dad sat in a comfy chair and talked on his cellphone, a witness reports. Simmons told us afterward: “School shopping can get expensive.” Yesterday the Def Jam founder tweeted he was headed to Washington, DC, for a “meeting with @BarackObama.”