Snap! I have a 9yr old brother as well.

Mine likes to play his DS *boring* That age they are into computers and gadgets.

For something creative, and if he likes cars, you could design a race track. If you have a big bit of paper or just tape lots of pieces of paper together and the two of you could design a new race track.

Does he have a scooter he can bring or a bike. You could go riding and take DD in the sling or pram.

i'll keep trying to think of things.