So my question is this: what strategies can I employ from the beginning of the game to accomplish this goal? Giving duchies to my dynasty members seems problematic over the long term because of the very real possibility of succession crises.
One thing I wanted to add: having your family members as your dukes is a plus. They mainly are going to cause you problems is if they have a claim to your primary title. If they don't have any claims and are in your de jure territory they will be very loyal to you. I typically work on keeping a group of unlanded family members in court. As long as your court size is not too big (I think less than 40? I try to keep it below 30 if possible), they will continue having children. After a generation or so from your original king, these members of your dynasty should have no claims on any of your titles, and be perfect for making into your dukes. Sometimes I use these courtiers up and end up giving a title or two to a favored son, but as long as you keep the number of troublemakers not so large you should be fine. Eventually their claims will die out. Also to keep your court size down, matrilineally marry away any male courtier layabouts who are serving no purpose, and similarly marry away any of the extraneous female courtiers that pop up.