I totally get wanting to have groceries with you in the hotel (I have two young boys myself). We always have breakfast at the hotel (or a pre-breakfast snack) and lots of snacks for during the day. Even with water, juice boxes, cereal and milk you might not have enough for a delivery but have you thought about throwing in some fruit or breakfast pastries or fixin's to make a PB&J sandwich for the kids? Or maybe a box of Ziploc bags for the kids crackers/cookies/other snacks?
Or what about buying AA batteries for cameras or any other electronic toys? They'd be cheaper than buying them in the parks but might bring you up to the minimum order... And since you're flying what about buying shampoo, lotion, sunscreen, etc. through Vons and that way you do not have to pack it into a suitcase or carryon?
Just some ideas....