How to split a 200 Amp main feed betweena cabin and workshop?
You can actually install two main disconnects below the meter. The NEC allows up to six main disconnects at one location so long as they are all marked as SERVICE DISCONNECT. These labels usually come with the equipment. 

There are several ways you can do this but I have found the simplest to install an MLO (Main Lug Only) panel and then install the breakers to each building. The only qualifier is that you cannot have any more spaces than would allow more than six mains (6-2 pole breakers would equal 12 spaces or poles). If you have a problem finding a panel to match that configuration Then just instal a 125A MCB panel install the breakers to each building below the main.

Hope this helps and good luck.