Cheech,

The short answer (for your needs, IMHO) is glow.

We had a student at our field with a Superstar EP electric trainer (his Dad had a second hand radio and was only willing to spring for the EP.) He could only fly the Superstar for about 15 minutes a day, since he didn't have a field charger or extra batteries.

$500 should get you all the essentials for a glow trainer that both you and your son could fly on any given day. Chances are you might find a friendly, neighborhood instructor at your local field who wouldn't mind loaning you his/her field charger so that you and your son could fly pretty much all day long.

My 2 cents,

-Matt