Unless I’m reading it wrong, you’ve got 16 weeks from date of application before you’re due to travel. I don’t think the queue is that long, at least not from what we can tell so far.
I’m also guessing that you’re in the UK, so you have the option to cancel and fast-track. It’s the 1-week fast-track option for child renewals. You’ll find threads about the process in this forum. I don’t fully recall the process, but I remember that there was a suggestion to report the documents lost as waiting for the supporting documents to be returned to you could take the same amount of time as processing the original renewal applications. Perhaps make sure from now that you have all the required supporting documentation (birth certificates, etc…) in case you’re going down the route of reporting the old passports as lost.
I would definitely call the adviceline for up-to-date information and to make sure any advice I get in this forum is valid