My strong suspicion is that the level of scrutiny (and hence documentation requirements) varies a fair bit, and likely in part based on country of principal applicant. Some countries have more of these attempts to get PR status 'for backup'. And for applicants from visa waiver countries or who have visited multiple times and/or with long tenor visitor visas, logically the effort is less likely to be invested just to be able to travel. (Looked at another way, many who have visas/waivers could have simply arrived in Canada and applied inland - another reason to not overdo it with scrutiny as fairly obvious that the sponsor/applicant are serious and want to work legally, etc.)
It's also possible that there is more scrutiny for eg sponsors who have fewer ties to Canada and would appear to have returned to their 'home country.'
But that said, too little information from reports here to draw firm conclusions. It's still wise to collect information and make modest preparations in the event that you get an additional documentation request.
For what it's worth, our application and documentation was somewhat similar to what you described above, and we had no additional document request. But we also had some additional info such as university preps for one child - and some aspects a bit less than yours - so I do not know what was decisive. (And all the family had long-term visitor visas and had visited multiple times, so possible the scenario above about inland application was the main factor - no idea).
