Hi Gary,
Your setup is pretty much spot on except for step 2. You can use the flowmap to color node to convert the velocity into a texture space aligned colour map.
I guess you could store the flowmap in the uvs and have multiple uv sets for different states but I think you could get away with a texture to do the same thing. Houdini should export extra uv sets without any problems. Make sure they are type float 3 vector and named uv2, uv3, etc and the fbx exporter should pick them up correctly.
And for vorticity/foam it's up to you. If your mesh has enough resolution you can use vertex colour or you can use another texture (or the spare channel since the flowmap only uses 2) to store the mask. That's what I did for Gears of War. Red and Green for the flowmap and Blue for a wind mask.
Mike