Hi!
First off welcome to the forum!
Your residencia card will not be renewed instead you will be issued with a plain A4 sheet of paper your Cerificate of Residencia…The government stopped Issuing Residencia Cards some time ago like maybe two years ago…so its back to the old routine of officially having to carry your passport everywhere. I dont know the answer to the query about the children. Again so far as I know its no big deal if the application is late….
So far as I am aware the form to be used is the EX16 some as you originally filled in.
The modelo de tasa cannot be downloaded; it is issued by the Police Extranjeros Dept when you hand over the application form. you take it to the bank, cough up whatever the latest charge is then go back to the Police…
Two steps forward three steps back! Ain’t progress a wonderful thing…