I wish to ask for some advice when it comes to building nested spatial expressions in PostgreSQL.  I end up with the same kind of problem many times when it comes to select more than one type of geometry.

The case I am working with now is related to it, is this: 

I need to find parcels that lay within a buffer zone around a numbers of waters and streams selected by their ID.
Waters are polygons, Rivers are lines.

I try to find a way how to write a ST_DWithin the polygons and the lines in one query to find parcels within the buffer. 

Is this a reasonable way to approach the problem or should I work with this kind of queries in a different way?