It's a tedious journey, though, Cockfosters to Heathrow. Allow a
good 90 minutes, may be safer to say two hours, and check which
terminal you need.

And, depending of course on the family's needs, dare I mention that it
might be worth consulting
https://www.tfl.gov.uk/assets/downloads/toilets-map.pdf



--
Robin
reply to address is (meant to be) valid