Hi Jo.
Start hanging onto the catalogues that are now coming out from places like Kmart, Target, Big W, **** Smith PowerHouse, JB HiFi, or whoever you local big electrical and electronics retailers are. There will be specials and package deals galore this month...
Good games for young boys (I have a 7 year old girl and a 5 year old boy) are:
Crash Bandicoot (pretty much any version, including the Crash Team Racing/Nitro games - many available as Platinum (cheaper) games now)
Lego Star Wars 1 & 2
Transformers !!!
any game based on superheroes - there are Spiderman, Batman, Superman games, Justice League Heroes, Marvel Ultimate Alliance...
any game based on popular family/kids movies - Shrek, The Incredibles, Teenage Mutant Ninja Turtles...
My son loves all of these! (daughter prefers Bratz Forever Diamonds and Sims 2 Pets....)