lumpy - 6:06 pm on Jul 9, 2010 (gmt 0)
a game making program designed specifically for kids is scratch, though even i find it difficult to use. i believe with some help your son could be learning to make games with the more advanced game maker. it is specified to build games such as pac-man, but as the user elevates his/her skill more advanced first person games can be developed later, with much skill. a pac-man type game could be created in about 1 hour of time with this program, it is at the following link :
it is a limited version, 20$ being the full price, but the features that come with the purchased version are not needed for anything your son should be producing anytime soon.