Different countries, different laws, different circumstances but the idea of a lump sum for child support sounds unusual. We're talking nearly two decades in your case. Make sure to really think this over. Could you effectively manage the lump sum over that timespan, or would a sum at regular increments spreading out the income be more helpful?
Yes, it is one to consider. If I understood it correctly, there is also the choice of getting the lump sum paid yearly or bi-annually, which I think could be useful if I need to pay for tuitions, school fees or any big ticket items annually.