Nature of bond in oxyacids of phosphorus
In general, I'm not sure double bond and coordinate covalent bond are mutually exclusive labels and depending on the specific chemical you're looking at, they might both apply.

My Reasoning:


Coordinate bonds are bonds where both electrons were donated by one atom. Usually, the concept of a double bond is used in the context of valence bond theory and coordinate bond is used in the context of crystal field theory. There is evidence for pi bonding in coordinate complexes (i.e. back bonding) leading to what could be called a double bond in valence bond theory.
If you look at bond length data you can usually determine if there is a double bond. (Or if you have some of the acid and access to an IR, you can do this yourself.) The CRC should contain reference bond lengths.


I 'm not an expert in phosphorous chemistry, but these could be helpful:


Structural calculations for many compounds, including a few acids 
Study on structures of phosphates, not acids