Oh boy, don't I know it about their deadlines. I already had a medical furtherance letter from my VO giving me one such deadline ..... dated 9 March and postmarked 29 March (thanks for stealing 20 days from me guys) asking me to do some further medical tests and have a report submitted within 90 days. ahaha. urgh. oh and they sent it to the wrong f&%$ing address too so it's kind of a little miracle that I actually received it (presumably my postman or neighbour recognised the name and made sure I got it) because if I hadn't then, well, you know. But when sending them the correction of my address via the case specific enquiry form, I received a reply informing me that they await stuff from me requested in a letter they have sent me dated 28 March, and presumably this refers to the medical furtherance letter dated 9 March but I have no way of knowing and naturally a follow-up CSE asking if it refers to the same letter and what is the ACTUAL deadline garnered no response at all.
I totally understand your frustration and fear. I am not filled with confidence either so far.
I actually just remembered that I had my husband go through our papers before submitting and fill in a bunch of N/As and NONEs by hand on the blank questions (I missed those when filling electronically) so we might very well have put NONE on that form for children but I actually have no idea since it was such a ridiculously long time ago and all. Fingers crossed.