Well one good thing about the Decathlon is that it will teach him proper take off and landing techniques. I bought that very kit with the thinking that it would be the best of both worlds.
Meaning that it would fly like a trainer and still be aerobatic when I wanted. Well it did neither very well. I tried a .60 two stroke and a .65 four stroke. It flew like it needed a 1.20 in it. It's a 7-8 pound airplane so don't expect much with a .46. Some people have that combination and love it. Just think Clipped Wing Cub with lots and lots of paint. Or as Allan put it, a Pig.
Sorry to sound so negative, but I've talked to many people at my field and they all feel the same way.
It is a very well built kit and is quite striking on the ground and in the air. It has no bad habits other than being really heavy.
Good luck. I wish you and your son the best.