Somehow I feel that Megha has fallen short on all the 4 aspects above.
I don't think she has ever bothered to explain to her children that Mohan is an important member of the new family, the family head, her husband and their father whom they must love and respect. For Addu, Mohan could very well be an uncle or a relative whom he has to tolerate for some time.
The second aspect of giving Mohan respect in front of the children is possibly the most important aspect. Only if she is respectful to Mohan in front of the children then only will they observe and learn and give him the respect he deserves as a father. But of late Megha has been ticking off Mohan in front of the children for additional expenses and even proving Mohan to be inferior to her in front of the children by bargaining better with the cab driver.
Thirdly Megha should indeed take the lead in full family interactions - encourage family games and activities involving all of them so that they bond as a unit. Mohan has been trying his best to interact with the children but Megha has not helped by keeping herself aloof and distant. For example when MNA were buying masks she too should have come out of the car and had fun with them instead of haughtily sitting in the cab.
On the question of friendliness and flexibility, I really don't know why Megha has chosen this time to become the headmistress of three schoolchildren. She is being bossy and strict , reprimanding Mohan when he calls Nanhi 'Chavanni', not smiling and forever rolling her eyes in exasperation as if to say 'hey Bhagwan main akeli parent in teen irresponsible bachchon ko kaise sambhaloo'. Why can't she be the fun loving and friendly person that we saw at the farmhouse.
Anyway I feel that the Bhatnagar family can be a fantastically happy blended family if Megha understands the subtle nuances of a blended family dynamics and plays the key role that she alone can play !