Is a 96 pound dog large or medium sized dog for adoption? also i have 5 month old son. would it be a problem?

i'm interested in a 5 year old akita male as in the link below. his weight is 96 pounds as stated in the link. So would that be considered a large or medium sized dog? also why isn't children under 6 allowed? i have a 5 month old son. He is too small to even realize that there is a dog in house. I am sure the akita should not have problem with 5 month baby. Would he? I understand children tease dogs and irritate them so that's why they say no child under 6. But a 5 month old boy is really incapable of all that.