MaxPass Question - buying it after you purchase tickets

Hi Experts! I haven’t had to purchase MaxPass since I am lucky enough to have a premier AP, but I am traveling with friends who bought a package that came with 3-day park hoppers. I know they can add MaxPass on the app, but I have a few questions.

1- Can they buy Maxpass for just one or two members of their family? They have two younger children who don’t like thrill rides so it may not be worth it.

2 - Can they buy just one day? Or do they have to buy Maxpasses for all three days of their parkhopper?

Any other advice? I used Maxpass for the first time in April and thought it would be well worth the $10 a day, but I’m not sure I have convinced my friends. The more options I can tell them about, the better! Thanks!

Because MP wasn’t purchased with the tickets, they can add it to what ever ticket they wish, for however many days they wish. Each day they want to use it, once through the turnstiles they can add it using the credit card they have on file. Let them know that they just to remember the security code (usually on the back of the card) if they do not bring the card with them. It usually takes a minute or two the first time. By the end of our last trip I had down to mere seconds. Have them add a credit card (if not already done) and the park tickets to their account on the app before the trip. It will save time.