Since the property in 'B' s hands is treated as self acquired property, there will be no need to take the signature of anyone, including his children, viz., There's no need to include 'D', 'E' and 'F'. as parties to the sale deed.

If A was survived by by  B and C alone, and if C had relinquished her rights in the proeprty by executing a registered release deed, then B becomes an absolute owner with clear and marketable title to the property.

In that situation, there is no necessity for his children to execute the sale deed jointly along with him.

The sale deed can be executed by B alone. 

You can add D & E to sale deed as witnesses only if they are major. If they are minor, they have to power to appear as witnesses of give a valid consent. If you want to be absolutely sure, you can ask B to obtain permission from Court to sale the share of D & E.

You don’t need to include his sons and daughter as parties to sale deed 

Dear Client,

As per the facts which have been provided, if B is the owner of the property then it is not required to include his children in the Sale Deed.

Hope this clarifies your query and requirement.

Thank you.

You need to make parties B, D, E and F. Mention all history of transactions and family.

Yes include them parties or seek noc from them

As you say A bought the land by himself, it became his self-acquired one. When he died intestate, it automatically devolved upon B and C in equal measure. If A's widow and mother have survived him, then A's mother, his widow, his son B and daughter C all shall inherit 25% undivided share each. Consent of sons D and E and daughter F of B is not at all necessary.

It appears to be the self acquired property of A and not any HUF property

so D, E, and F are not required to be parties in the sale deed