I have boys, and the most important things they need to know and witness are as follows
1.) How much you love and cherish their mother: My wife is a great lady and a bit fucking looney (normal, all women are) but my boy see's me tell her how much I love her, help her with any and everything when she wants it or needs it and that I put her needs before my own. Boys really need to see this shit as it teaches them about respect and shows that mom and dad are a team and that there's love int heir home.
2.) Dad might be capable of beating your ass in such a manner that you should have a deep seeded and lifelong fear of him: Little boys are like tiny savages and in more cases than most would like to admit the non-vocal threat of immediate and mind altering violence is all that will keep them from doing something extremely stupid that can lead to them harming themselves or others due to their own lack of understanding about how the world (or in our most recent case, a log-splitter) works and crazy eyes from dad will be the thing that keeps them from straying too far from the path of not getting me any expensive fucking hospital or property insurance bills
3.) Nobody likes a cry-baby: Don't flip shit when you're mad, sad or frustrated, thats how people learn you can't handle yourself and will either mock you or take advantage of you. Handle your shit before someone hands it to you