US Passport Child Renewal London Help

Hello,
I've lurked on here off and on through the years and finally decided to join to get help.

We are finally getting US passports renewed after they expired about 5 years ago. 

2 children aged 12 and 16.
I only see the requirement for the passport photograph.  But last time we went, we needed to supply 5 photos for each year they were alive.  Is this still required?

My eldest is dual UK/US  national.  We are traveling in Feb to visit family in the US.  His UK passport expires in June 2023.  Will he be OK to get in and out of UK?  I wanted to get his UK passport renewed after the Feb trip due to the costs.  To get to London by train now is unaffordable and trying to spread out the cost.

Thanks for any insight.

You are correct, you no longer need the "progression" photos for renewals.

Yes, you can re-enter the UK up until the day of expiry on the passport.  No need for the passport to have 6 months validity. 

That is fantastic. 
The 'progression' photos were a huge pain.  Thank you for the insight on both points. 

Now, I just need to find a dog sitter.

Apologies, as I have another questions. 

For those Born Outisde the US.
Do I need to do the Affidavit showing all your US citizen's parent's residence in the US before your birth?

 I did this when i registered their birth but did not do it after that...
I can't even remember what I put.  Its been over 16 years.

Thanks