The Flexner bio seems to be pretty popular but is 448 pages so may be too long.
Either the Ellis biography or the Brookhiser bio (I can’t remember which one) does have a bit of speculation in it. He suggests that George Washington may have had an affair for instance. Some moms chose not to use it for this reason.
I did read a few chapters of the Brookhiser bio and found it a bit dry myself.
The Ellis biography has a lot more 4-5 star reviews than the Brookhiser option.
I love Foster’s books but don’t feel like it would make a good selection because it jumps around so much, therefore would be comparable to a very brief GW bio once all of the sections on him were added up. I wonder if Heritage History has any good choices? They probably have Irving’s GW bio but it, too, is rather long.
Based on all of the choices, I would probably go with Flexner’s bio if time permitted. It is long, but not nearly as long as The Real George Washington and is said to be highly readable and enjoyable to boot. If you are on the AO forums, I would do a search for Flexner and read what other moms had to say.
The best option would be to download a sample of both and let your son choose but I don’t think the Flexner bio is available for kindle. 🙁 You could do this for the Brookhiser and Ellis options though. I think they are both available for kindle but I could be getting biographies confused.