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Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 100,399
Will you have UK national health insurance coverage while there? If not, check whether your policy (presumably as an employee benefit) covers you on a personal trip abroad of this length. A lot of USA managed care policies do not. Note that your child is likely to need routine medical care such as shots if you're away for three months or more, although you might be able to plan around this somewhat before leaving.
If your child currently goes to preschool etc., not doing so could be a big adjustment if there's no similar program available in your location in the UK.
When you say north central USA, how bad is COVID-19 where you are? I'm guessing Iowa or Missouri (but I'm not sure the latter would be north central), based on equidistant from ORD and DFW, although at first I was thinking WI, MN, ND, SD, etc. which are places where either infection is raging or is expected to get much worse in the next week or two.
If the goal is a nonstop to LHR, there might be additional airports if you don't necessarily insist on Oneworld.....or you could consider connections if the schedule is good.