+1(514) 937-9445 or Toll-free (Canada & US) +1 (888) 947-9445
Just to note, nothing prevents applying for both at the same time. The PR application would be needed anyway. Since they are under 18, timing or availability of open work permit is not an issue, so the outland app can just be allowed to proceed until done.

Good Idea !
It will cost more for 2 applications but also increase your chances.