If you're organically hitting 140,000 SQM each year, what is the purpose of choosing bonus SQC? Even if you chose the bonus SQC at every possible milestone (which it doesn't sound like you are given the mentions of gifting status) you'd accumulate 22,500 more SQC, giving access to the 150k and 160k milestones, which would give you some combo of points, some status passes, or a $250 gift card. No matter what you choose, you could have earned more by just choosing those items at previous milestone benefits.

Grabbing at least enough PRs for your kids to use on their TATL flights seems like a no brainer to me. The cash in pocket savings are going to be pretty huge. Sell/trade them your points (looks like you should be generating 1M+ per year from your flying alone) at a good rate if need be.

With some advance planning and/or flexibility you should be able to fly on AC metal for something like:
TATL J R/T = ~300,000AP.
TATL PY R/T = ~170,000AP.

2x TATL J is 300,000 + 2x PRs. ~$10,000 saved in cash
4x TATL PY is 340,000 + 4x PRs. ~$8,000 saved in cash.