Downloaded one of you pics and those spots are definitely hot pixels caused by long exposure times.
If you do a normal shot (non dual iso) and activate long exposure noise reduction in Canon menu, the colored dots are probably gone...
Long exposure noise reduction automatically takes a second picture with the same exposure time, but with a closed shutter, this second picture is used to extract from the first picture and removes most of the hot pixels.
I don't know if long exposure noise reduction can be used with dual iso pictures...I'm not sure if the second picture get's extracted from the first raw file

If not, you can process you dual iso pictures the normal way, but in the end use a different raw editor to process the DNG.
RawTherapee is free, open source software, that has hot pixel remover build in, as wel as different debayering options, my opinion is that it works better for dual iso DNG's then Lightroom.
But there are probably a lot more free/open source options available