@MRX
At public mobile each account needs a separate sim card and a separate email address. Using one gmail account (preferably the persons who is managing the accounts) and then two aliases which satisfy pms requirements but will send all emails to you (the main gmail account holder.)
While this should help you overcome the promotion issue you may find to manage the accounts it's more of a hinderance if the accounts need to be managed separately in the future and still requires you to log into each account separately. I would just create two additional emails similar to the original ie j.smith@gmail.com then j.smithmom@gmaiil.com and j.smithson@gmail.com and have the moderators change the emails on each account in the future. You could create each password in a similar vein so they are easy enough for you to remember but still difficult to guess. This will keep community accounts separate and individualized if one or more of you participate in the community and hope to earn a community reward to be linked to each account separately.
It will still make it easy to seek community support or moderator help when necessary. Remember to use a referral code for the first account you activate (msg someone here privately if you don't have one) then use the first accounts referral code to activate the second one and so on.... consider each account users data needs carefully so you select the correct plan for each user as yoù risk losing the promo data add ons if you need to change plans before they are fully consumed. $40/5gb plan is probably the best bang for your buck but might be wasted on someone who only needs some data then saving $5 might be worth activating on the $35/2gb plan.
As mentioned by @hairbag1 you can have two payments occur on one day and the third the following day (by activating after midnight) or activate them on consecutive days.
Contact the moderators as suggested to ensure you can have the promotion applied on all three accounts. (The original and the two email alias accounts.)
