We have travel planned to Sweden and the UK in late November and just realized our 2 under-16 year old kids passports expire in early January. It seems UK only requires the passport to be valid during our stay, but Sweden requires 90 days validity, which we won't meet.

Since the kids are under 16, I can't find a single post office with an appointment near me over the next couple of weeks, and am concerned that if we find an appointment in mid-September or later, the renewals won't be processed in time for our trip.

Any ideas on how we might best go about this?