My thing when flying long haul is to always take the last flight out, or as late as possible.
If going forward it means you sleep through the night and and if going back, as you will be to the US you'll leave late and sleep on the plane hopefully and then arrive in the evening and can sleep again a few hours later. Might mean you are up a bit early the next morning or lie in because tired from journey etc, but I find it works well for me like this. I've flown both ways, US and far East and Australia. Not always with kids, but have flown with kids to the US before.
You can also try leaving early, so as to have LO awake on the plane (not ideal on a long haul flight at that age maybe) and then get there, tough out till the evening and just have an early night.
TBH long haul travel usually messes with small childrens clocks and you just have to deal as it happens. I always prefer to fly at night so sleep is at least something that should happen once child is tired enough. If you are waiting round an airport in the evening, LO can be awake, sleep or something in between. Once on the plane and everyone has had their evening meal its lights out and kip time normally.
As for when you get there, just get into the time zone as quickly as possible. Let LO sleep in if it will help bring his body clock round on the first day, or go to bed a bit earlier for a few evenings. And then don't let him sleep in too late in the mornings. He can nap in the day if need be, but letting him sleep in means he won't settle into the US timezone as he'll be working on UK time.
Hope that made some sense.