OT but... Hi Tan!
Sorry Mel LOL. Quick question, what does your DH do with your DS when he is in the room with him? Natty used to want me to pat her bottom, sing to her etc. This was stringing bedtime out for a long time even though everything I was doing was low key (ie we weren't chatting or playing games). Lately though our routine is stories, tuck her in, kisses & quick chat about what's happening tomorrow then I 'sign off' by saying goodnight and I love her. Then I sit down at the end of the bed and wait. I either doze (and sometimes DH has to come in and wake me up, LOL!) or I play a game on my phone. I just relax but Natty and I don't interact at all. This seems to be all she needs and without me singing or patting her she is actually better able to get to sleep.
Not sure if this is relevant to your situation (perhaps your DH already does this or perhaps this might be a bit sad for your DS) but it has really helped our situation and Natty adjusted to the change easily.