Subpanels don't matter. You just need to add the loads.
Since you're talking about multiple dwelling units, then there's a very good chance your load calc will exceed 200A. But a load calc for each dwelling unit is the way to start the whole design. Either teach yourself how to do it (use the alternate method) or get an electrician to do it. It's not so hard to a load calc, although I've only done it once or twice; most of the work is listing all the electrical loads, the subsequent math is simple. There should be free worksheets/spreadsheets available to help you.
Once you have the loads, one basic design question is whether to run service conductors to each building (I assume the cottages are detached), or to run feeders. The only real advantage to running service conductors would be that you'd save one wire, so I guess feeders are probably better (haven't thought much about it).
If you end up with (2) 200A panels, one for the cottage feeders and one for the main house, then there's no need to have them together, if you have a main disconnect by the meter. E.g. outside could be meter, main disconnect, subpanel for cottages; inside could be subpanel for the main house. Depending on the load calc, one or more large outdoor loads (A/C units) could be fed from the outdoor panel, if convenient.
Cheers, Wayne