@nonemmet
I totally agree with making sure families sitting together lets make that clear. But if a family are one of the last to check in and you have 50 other familes onboard it can become very interesting on boarding. So my point is the CAA only give guideance on the situation like using words such as " should ideally" and "should take into account". Personally i would not seat children away from their family unless over 12 and only if it was the next row. As you mentioned the viking aircraft are actually C-reg and are operated by sunwing airlines of Canada. So the viking flights would be ruled by sunwings SOP's and SEP's ( i've worked for sunwing previously). I found some of the candian rules quite relaxed like - infant lap belts for under 2yrs were optional! (well not on my flights).
So i will always advise families to check in early and get seats together to save problems onboard.