Downstream of a STB, coax is only good for an SD signal - no use for HD - builders should know that coax is mostly useless these days... If you want HD, you'll have to go with HDMI (and an HDMI splitter) or component video plus some form of audio, plus splitter. I'm not sure if the PVR you are looking at allows for simultaneous output of component video and HDMI... Please advise make/model. Also, are you going to have an AVR and other equipment, or just TVs for audio?
Since most people don't want the same signal/channel on two different TVs, you're likely better going with two STBs, one for each TV.
In addition, if you want the Shaw Direct HDPVR (like the 630), you need two coaxes to feed the signal from the dish to each PVR. These sorts of set-ups should be planned thoroughly before
the building/drywall is complete. The days of a simple coax feeding a TV directly have been gone for a long time in Canada, especially for HD.