I'm not certain it's still possible. If it's possible, I would consider the following based on your last reply which looks pretty accurate as far as tax free space for conversion:
1) How long will you be able to claim the kids as exemptions?
2) How long will they be eligible for the child tax credit?
3) How much will you need to move out of T.IRA and how long is your time frame to do so?
I would map it out like this based on current tax law:
Year 1 - 10 move $47,500
Year 11-14 move $30,000
Year 15-18 move $21,000
Year 19-24 move $30,000
Year 25-30 move $22,000
Deductions and exemptions will be indexed for inflation. Tax laws will change. You might earn some other taxable income. Your kids will move out. Before they move out, you might be able to claim college tuition credits. You will have no idea how much the T.IRA will grow before you move it to R.IRA. Move your holdings that have declined in value that you expect to increase in value. If the market tanks in any given year, consider moving $80K and paying tax on half of it at an effective rate of 14% just to ensure you can clean out the T.IRA before RMD's kick in.
I know that's not what you were asking for, but since you're so close to FIRE I thought I'd outline my rough plan in the hopes it could help you think through all this.