Can anyone whose children already own these explain to me do they take batteries - like the Gameboy Advance or is there and inbuilt rechargable battery with a plug in adaptor for charging - this is what someone told me tonight and we bought our childrens in Florida in August, and I've already wrapped them up - would hate to have 2 upset children come the morning of the 25th that can't play because we don't have the right adaptor! Can anyone help. Thank you