Hey amijee --
My DC have been 4.5 mths, 9 mths, & 3.8yrs on the various trips (that's 2 children on 2 trips) from the UK to the US. Guess the experience with the 4.5 mth old most relevant -- as he had similar sleep to your DS at the time
(BTW the 3.8yr was the best , plugged her in to the TV for UK-US leg, she slept most of way back, 2 days of delayed sleep, then back to normal -- leaving me to deal with DS )
On the way over, I stick to their schedule, except add in a extra naps/feeding to cover the time difference (BTW you don't say where you are going -- I did a 5 hr time shift to midwest). We landed about 6pm, so followed the bedtime routine and put them to bed "normal" time in the US. They are so knackered, they slept fine. This seems to set them up for US time, as both then proceded to wake at "usual" times. If they happen to wake early, I'd treat it as a night waking.
Coming back is a bit different. If at all possible, follow as much of routine as you can on the plane with any props (e.g. sleeping bag, etc) Your DS should be able to fit in a skycot. Hopefully will sleep for you -- though you may consider having your DS sleep with you, as if the seat belt light goes on, you have to remove the baby from the cot. This is what I did with my DC. DS managed to sleep for about 75% of flight. Try to get some sleep yourself. Then, when you get back, if you need a nap, have one, but only a short one (no longer than 2 hrs for you) and get into the daylight. See how DS goes, with sleep, try and wake near normal times. Follow bedtime routine at normal time if poss, but it may be delayed. But I found with my DC the first night back, they went to sleep 3 hrs later, second night 1.5 hrs later, and the following night on time. I did wake them close to their "normal" waking time though.
That was long, but hope it helps. Let me know if you have any questions.