I’ve had several Boxers- they are loyal and LOVE kids, they can get very protective of their humans against outsiders
but their bark can be worse than their (under) bite. Their appearance alone is enough to scare off bad guys.
Three is plenty young to learn new tricks and to bond with you
The only problem I had was that they were cancer prone and died young (ages 9-10)- but our lives together were good all around! Go for it! Feed them only healthy hi quality dog food.
Nutro’s “Ultra” line of food has extra ingredients that are supposed to help prevent cancer in dogs. I adopted my little terrier from the pound back in November. She has a small fatty tumor on her head. I switched her to Ultra (from Eukanuba) the first dish she picked out all the Ultra and would not eat the Eukanuba. It was only a month ago that I found out about the anti cancer stuff in Ultra.