Welcome to FT!

The basics: Status is earned based on miles flown between 1 January and 31 December, plus certain bonuses offered by some of the DL AmEx cards. Thus, if you're not earning 25K Medallion Qualifying Miles with Delta during a calendar year, no status. If during 2011 you earn Silver Medallion status, it will be good for all of 2012 and through 28 February 2013.

For redeeming miles, it's harder, especially since you can't pool the miles without paying transfer fees. Do you and each of your kids have 37,000 miles? If so, everyone would have enough miles (theoretically) for a round trip within the US. If you let us know where you'd be flying from and where you might like to go using your miles, we might be able to give more specific advice. (Award tickets to Europe will start at 60K round trip, so it would take a couple more trips for everyone to have enough miles to book such a trip.)