I recommend you use one acid or the other, but not both. People have reported having problems in their soap from using both. I don't recollect the exact problems, however -- perhaps someone who has done this will share their experience.
What I do know is too much of some kinds of salts (as chemists define the word "salt") in soap can make the soap soft and rubbery. The salts can also migrate to the surface of the soap bar, creating an unattractive white salt layer. A 2% dose of citric acid plus vinegar is a fairly high dose of total salt. There is a good chance these problems will happen.
From a safety standpoint, yes, you can add the citric acid to the vinegar, mix until the citric acid is dissolved, and then stir in the dry NaOH.
Go slow and keep stirring when you add the NaOH until you know how the mixture will behave.
By the way -- Do you realize your vinegar is no longer vinegar after you put it into the soap batter? If you want the benefit of vinegar for your hair, you need to rinse with vinegar
after washing with the soap.
Vinegar + NaOH => sodium acetate
Citric acid + NaOH => sodium citrate
More:
https://classicbells.com/soap/soapystuff.asp Scroll down to "Acids and Salts"