I am preparing for the GMAT.
I have a 3 yr old kid. My husband is also studying for Gmat.
Is it possible for us to take the child, mother - in- law with us ?
You have not mentioned the country. I assume that you and your husband plan to come into The United States on a F1 Visa. In this case, you both will need a F1 visa. You can get your child as a dependent(F2).
Mother-in-law is considered a relative and hence, as Jerx has mentioned, she will need a B1 visa(separate process) and can live in the United States upto a max of 6 months for one entry. It is little challenging to obtain a B1 visa for her based upon you/your husband's F1 status.