-you were married in your home country, had children and you were divorced from your first wife.
-you subsequently married a Canadian and your Canadian wife sponsored you, you declared your children as non-accompanying and they had medicals at the time.
-You now are separated from your Canadian wife and plan to divorce. You already have Canadian citizenship.
-After this, you wish to sponsor your children from your first marriage (I assume they are all still meeting requirements for age? Are they / have they been your dependents throughout this whole period, receiving financial support from you?).
-AND you plan to remarry your first wife and sponsor her as well (or is the planned marriage to some other person)? Or will she (first wife) allow you to sponsor the children separately and she will not come to Canada?
I don’t see any obvious issues with sponsoring your children.
Or even, in principle, re-marrying and sponsoring your first wife. The situation is a bit unusual but not unheard of, assuming that all these relationships have been and are genuine. You may get some additional scrutiny regarding your ‘re-started’ relationship.
I honestly do not know situation regarding processing times, your urgency, etc. It’s possible it would be advantageous in some respects to sponsor the children separately but only speculation and only you know the full story. Consider consulting a lawyer or immigration professional if you have concerns.