Is one to buy a set of Hashanos for each family member?[1]

From the letter of the law, there is no requirement for every family member to perform Hoshanos. However, the widespread custom, as well as the Chabad custom, is to purchase a set of Hashanos for each family member, including one’s wife and even small children.[2] If the child is an infant and cannot hit the Aravos themselves, then the parent is to hit it on the floor on their behalf.

[1] See Piskeiy Teshuvos 664:3

[2] Otzer Minhagei Chabad p. 334-336 and that so was custom of Rebbe Rashab and Rebbe Rayatz; The Rebbe prepared Hoshanos for the Rebbetzin; See Piskeiy Teshuvos ibid footnote 10 that so is the custom to prepare Hoshanos even for newborn children and it is based on an old custom found in Minhagei Wormz, and is similar to the custom today of Machatzis Hashekel and Kaparos