Hi thanks BelRed,
Thanks for the info, that was very helpful. I confirmed that the IR-1 does not apply, his Canadian wife will need a CR-1 (or "Conditional Resident Spousal" visa (essentially a 2 year conditional green card) which is meant for spouses married to the US citizen for less than 2 years. I also did a bunch of investigation and confirmed that it is bad to apply soon after entering as a tourist, and *for sure* not sooner than 90 days or it is automatically "suspicious". I also found out that it is better (or at least less problematic) for her to enter as a tourist and then file the I-130 than the reverse, because if the I-130 is on file, the border immigration officer can see that, and may outright deny entry as a tourist. But it is still somewhat risky (even without filing an I-130) to enter as a tourist -because technically she has "immigration intent" and she is not really a tourist (unless she really was going to visit her husband as a vacation, and still come back and live separately in Canada for some time).
The good news is that it appears there are 2 valid routes I can find. First, my son files an I-130 (online) from Canada, then uses the acknowledgment receipt to file an I-129F to petition for a K-3 Visa. Apparently that can be quick, and with a K-3 Visa she has 2 years to cross the border either way, including while the I-130 is being processed (otherwise she may have to stay in the US for that portion). She can also work under a K-3 Visa during this time (but EAD approval for that may take 90 days). With a K-3 visa she can also file an I-485 in the US once the I-130 is approved (or maybe earlier not sure). So the K-3 seems to be the way to go, to legally and honestly enter while waiting for a CR-1. Once she has the CR-1 after 2 years she can get a regular green card and from there US Citizenship after some time.
The 2nd valid route seems to be even better - just file for a CR-1 directly while in Canada -- at the local US embassy/consulate. It is not always allowed, and is usually only for US citizens living in another country for some time (which they have to prove), but it may be possible, and may take only 1 week to 3 months. Then she can enter directly as a CR-1, work right away, etc. I will be calling the local embassy tomorrow to see if this could work!