We had Barley, who, at 7 years old, we introduced to Bramble. Initially she was horrified, and as an unspayed bitch, we were conscious of the risk unless we had him 'done'.
Her first season, when he was about 6 months old, we had him sleeping in our bedroom, and they were kept apart when not supervised. He was always quite sweet however, and whilst she would encourage him to mount her, he would go at it from the side and ride around on her, saying 'This is how ya do it!!' much to her frustration and disgust!!
We had him castrated at about 11-12 months, and his behaviour hasn't changed at all .. he is still cheeky and lovable, still rides round on the side of her if she lets him and is a total little innocent!!! He had a white seal toy when we first brought him home which was the same size as he was, and he used to shag that, but thankfully he hasn't felt the urge since those baby-hormones left him ...!!!
In retrospect, I wish I had had Barley spayed, since she has had a couple of op's related to mammary cysts, the last one revealing cancerous invasion, so her time is finite .... at the time, I was either too stubborn to put her through a GA with no good reason or I didn't pay proper attention to the information I got (or maybe didn't get - I can't remember anyone saying about the percentile probability then like they do now ...)
If you get your little boy castrated he will be absolutely fine with your entire bitch - Barley washes Bramble's face all the time and cleans him all over if he will let her! You still need to keep a watching eye on her when in season of course, because of other dogs, and also her mammary glands (check regularly for lumps or bumps) and also pyometra which presents as a smelly discharge associated with fever and general discomfort - this is a uterine infection which can be fatal if not immediately treated, and (as I found with my old Lab) can sometimes masquerade as the onset of a season, to the extent that dogs are drawn to the bitch simply because of the discharge, which, if it happens at the expected time, can also fool you ...)