Yes your boys are lucky, having 2 myself, but still two small to enjoy it... I wish I will have the patience later on to paint for them a full army, actually I would need two armies, one each!
Solid skills for a table top job, +1 for the mold lines. It doesn't require much efforts compared to painting and increase the perceived quality tremendously, Zab advice works in most of the case, knowing that ABS glue dissolve the plastic, but be careful with fingerprints.