Originally I was thinking that printing out a paper wallet would be the way to go, it's safe, just don't keep a copy of the private key or you'll end up in hot water - If you buy a reasonable BTC 0.01 (about $ 6.50 at the moment) they can put it in a safe place like a family bible or the high school year book, something they keep safe, but don't look at all the time. They can then come across the paper wallet in multi years time and see how much the value has appreciated in those intermediate years.
But then I also thought that you could install a BitCoin Wallet that doesn't download the entire block chain, this way they can experiment with sending each other (I presume you're going to give out to the parents, siblings, children Aunts & Uncles and or cousins all at the one time) the BitCoins. You can walk them through the receiving their first BitCoins, then guide them through sending each other coins one afternoon at a family gathering.
Then when they've played with BTC 0.01 for a while drop a hefty BTC 0.1 (or more!) into their wallets each and see their beaming smiles when they realise how much you've just given them.