Two items from our Swedish friends at IKEA that will make any picnic perfect:
Sommar picnic tray ($9.99)
and blanket ($29.99).
We tested these out recently at our favorite Wednesday night happening, The Brookline Summer Outdoor Concert series. They were both a hit and super-handy. The blanket's lined with some water-proof like material on one side, cheapo fleece on the other. And the tray just happens to fit a (camouflaged) bottle of wine, couple of cheeses, bread and snacks perfectly.
Not only can you sit comfortably and listen to Beatles covers while your kids whirl dervishly about, you can also look rather stylish with your new equipment.