I ended up making a bunch of kings. They are currently easy to manage, but that's mostly because my Prestige rating is through the roof (13K, and my current character is 60 years old so could conceivably live another several years yet). The real test will be when "I" die and control my heir. I gave him a full Duchy to control for now to build up Prestige and gold... but he insisted on going to war against Cairo and ended up getting beat to snot.

I've taken to Educate-ing any underage kings or dukes to get the +20 approval from them when they come of age.