The simplest way to handle this is probably to use XSD 1.1 and use an assertion on the parent to specify that there must be exactly (or at most) four children. You will also need to make each child of the all-group optional, since thirteen of them will not appear.
The best way might be to redesign your XML to work better with your schema language instead of fighting it. It's hard to give advice on that, though, since your example is abstract enough to make it unclear why you are imposing the requirements you mention.