The short answer is:
you can't have multiple (not nested) dataviews with different entities and a context datasource on a single page.
Longer: To achieve what you want to do you need to somehow link those entities together (if they not already have some link in the domain model). So what you could do is to create a single master entity (this could also be non-persistent) with an association to all the entities you want to show on your page. Then have that entity in the main dataview of the page and show all other dataviews/entites via association from that master entity.
I'm almost sure someone will enlighten you with some nice pictures of datamodels and pages if needed.