The father may not be present at the certification of the donation contract, but he must write a statement of consent to the notarial act and notarize it.
The sales contract should be notarized. After all, in the event of misunderstandings between the parties and, say, an appeal to the court, it will be the basis for the consideration of the case, and not the deposit.
You don't need to redo it yourself. That is, after buying an object of immovable property, it is not necessary to order a new technical passport, you can continue to use the data of the technical inventory that was carried out earlier.
A note about the change of owner is made (at your request) on the technical passport (this is not mandatory). During the transaction, as a rule, from the new owner, the notary receives a statement of agreement with the technical conditions of the object specified in the technical passport, and the transaction is carried out according to the old technical passport. Conducting a technical inventory with drawing up a new technical passport is required in case of re-planning, changes in other technical conditions of the object.