Replies
WhatsApp replies from contestants and parents. Answer them in WhatsApp; free-text messages can be sent for 24 hours after someone replies.
Automatic reminders
Once a day (around 9am UK) the reminders below go out by themselves on the channels you choose. Start with a dry run: it records who would have been messaged, without sending.
Reminders due
Worked out from each contestant's record and when they were last messaged. Sending ticks them off.