On a side question, how old are the boys, I think you mentioned it at one point in this thread, but I don't remember? As to the nails you might want to grab one of these from Harbor Freight
30 Magnetic Sweeper with Wheels We bought one a few years back after having the house re-roofed, last year we loaned it to my wife's sister who had just finished a remodeling project and just in pushing it from the backdoor of the house to the car to take it over it picked up a couple of pointed screws and a couple of washers in the grass by the driveway. (they also make narrower / cheaper ones)
Ike
p.s. if you want to barrow ours let me know I can probably get it close enough for you to easily pick it up from my sister in laws house, by maybe this weekend, my nearly 13 year old niece is doing the 2 week over here, and 2 weeks over there thing between her mother's house in Cypress and her father's house in Louisiana for the summer.