Ricevuta for get in and get out Italy after Visa expired

Hi, I hope someone able to enlight me.

I am in Milan for study from Feb - Sept 2019. I bring my son and mother in here. I already apply Permesso di Soggiorno for me and my family and we get appointment on 27 August 2019. To enter Italy, i use student visa. For my family, they use a tourist visa that valid until 16 August 2019, but their 90 days would be over on May 2019. This is our first time applying. My question:
1. Is my family able to go home after May and come back to Italy before their appointment only with the ricevuta? I'm afraid because of overstay they might get penalty or even ban to get in Italy again.
2. What if we decided not to come at appointment? Is there any concequences?

based on information that I get, because my appointment is 1 month before my study over, I will not get a residence card (process to get the card is 3 months minimum) and I would only get a piece of paper, stated that I am allowed to stay here until Sept 2019. My family apllication is based on my permit, so if I dont get the card, my family might not get one. So right now I only could think of the longest time I can have with my family before they have to go home, without violating any rules in Italy.

Thank you.

New topic