So back to your question.
So a total of 6 people. In 2023 this would be $50,350 per year.
See https://www.uscis.gov/i-864p
You should also read https://travel.state.gov/content/travel/en/legal/visa-law0/visa-bulletin/2023/visa-bulletin-for-september-2023.html
As you can see cases from 22APR07 or earlier are now being taken up.
Some people will tell you;
2023 - 2007 = 16, so a 16 year wait. That is not realistitc.
* 5 years ago, cases from 08JAN05 or earlier were being taken up: https://travel.state.gov/content/travel/en/legal/visa-law0/visa-bulletin/2018/visa-bulletin-for-september-2018.html . So in 5 years the date progressed 15 months. IOW 60 months of duration had 15 months of progress.
* what we are seeing is that even when a filing date becomes current, cases languish in NVC for years because a visa number is not really available. It appears the State department is manipulating the visa bulletin to show a more optimistic view.
Thus a realistic wait estimate is
(2023 - 2007) * 60/15 + 3 = 67 years. Assuming 3 percent annual inflation, you will need to earn
50,350 * 1.03^67
= $364,832
Whether their kids will age out, depends on their age today. Looking at the date of filing chart for F4, it is 11 months ahead of the final action chart. So I would expect I-130 approval in (2023 - 2008) * 60/15 = 60 years. 64 - 60 = 4
21 - 4 = 17.
So any kid 17 or older will age out for sure. Kids under age 17 have a chance unless USCIS plays dirty and approves the I-130 too quickly.