I'd just add the brood to a 3rd brood box and cull your oldest (or poorest performing) queens. You'd end up with a hive that is 3 deeps high and them break them into 2 hives (or your target number) next spring and add fresh queens. You can winter them as doubles, singles or even 5-frame nucs with a little TLC. If you want to keep your queens, you can probably winter them without too much trouble. If you're in the valley (I lived in CA from 1975 to 1990) or where you get 50 degree or better days every few weeks, you should be able to winter your nucs without much or any prep work. If you're colder, you could butt them up against one another (to minimize surface area), wrap them in insulation (the silver stuff they use for water heaters works fine), reduce the bottom but crack the lid (I make lids with an upper entrance) to vent carbon dioxide and water vapor out the top and set them someplace with southern exposure.