Hi vera,
 
I just bought a birthday present for a six year old boy (who's also smart and athletic).  It was a tough decision because I knew he already had every kind of ball and net available!
 
We bought him some walkie talkies, an outdoor exploration kit, and a bug vacuum.   He LOVES it!  It's a great way for him to use his brain while running around outside.  We bought everything at Target (on a great sale) but I'm posting links to Amazon in case it's easier for you to shop online.
 
Hope this helps!