A funky watch and/or voucher for a shop each? (sports shop for boy, clothes shop for girl?) oo I love a good watch
http://www.argos.co.uk/static/Product/partNumber/9249532/c_1/1|category_root|Jewellery+and+watches|14416987/c_2/3|15701267|Children%27s+watches|14417280/c_3/4|cat_14417280|Boy%27s+watches|14417281.htm
http://cgi.ebay.co.uk/LADIES-OASIS-WATCH-MIRROR-%26-KEYRING--NEW----tatty-box_W0QQitemZ280577069248QQcmdZViewItem?rvr_id=178022703269&rvr_id=178022703269&cguid=a90d741112c0a47a44747fd4fff89cb6
Or take the p and send them a kiddie selection box and a pair of socks each