Thanks.... He wants to play football next year and could use a little size....
Don't force him into gaining.
He is only forteen, i don't know how many ripped and shredded 14 year old muscle freaks you have seen, but i haven't.
Get him a good diet, whole foods, lean protein, chicken breast, yoghurt, slow carbs like brown rice, whole wheat bread and whole wheat pasta. THis will be enough.