LOL Nice question. check out thsi link this contains all the party ideas....  My wishes to your 13 year old Kid...http://www.google.co.in/search?source=ig&hl=en&rlz=1G1GGLQ_ENIN312&=&q=party+ideas+for+thirteen+year+old+kid&btnG=Google+Search&meta=lr%3D

• You can ask your boy how he wd like to celebrate his bday...
• You can arrange/sponsor for a movie+lunch for your boy and his friends.
• At home you can cut the cake and the regular bday party wd be fine. You can buy him some gifts that he has been asking you for a long time.
• You can order pizza and coke and arrange for sleep over of your boy's friends in your house. Get them some dvds to play all night !

Yeah maybe check with him what he'd like to do on his b'day..kids today know exactly what they want to do n also whom they'd want to invite..13 is also when they r embarrased abt so many things..mainly their parents n a boring party..