This sounds like it could be a fun start of a game. All the small "errors" you do in the beginning make the games a lot more interesting imo. First of all, landing any sons is really not necessary. They'll bitch about it, but so what. Your heir gets your titles, and as long as you have primogeniture, younger sons exist solely as a safety net in case your eldest keels over before you do. It's often a better idea to give land away to people not in your bloodline at all as you increase the power of people with claims to your titles by doing so (giving to family). Marrying your heir to someone with land or possible land might sound like a great idea, but there are several problems. If your heir's wife dies before your heir does, your heir's heir will take over your heir's wife's holdings (if your heir's heir is the same person as your heir's wife's heir). That means you lose control of him until your heir dies. He could get up to all kind of fuckery until then. Like marrying a girl with three chins. You also already lost control of your grandchildren until your heir dies.

If you want to narrow it down, ck2 is a lot about making a smooth transition at your death. As it is right now, when you die, you might have a son that's done all sorts of dubious life choices in his own domain, with a pissed off brother as his vassal, holding very strong claims on his titles. His wife will be off in Wales with the children and you can't do anything about it. Except kill the wife and then yourself - which is tricky. There might be a period of 80 years until you are in firm control of your closest family again. Have fun! (And you probably will).