@Anonymous User You used to be able to do this on the website but now they've redesigned it the certificate filter has gone. You can still use the genres to filter by family or Disney which will contain most of the child-friendly films NOW TV has to offer - link here
https://www.nowtv.com/gb/watch/movies/explorer?genre=family
or most apps also have this in the Movies > All Movies section.
Or alternately you can use the third-party website run by forum regular @Anonymous User which does allow you to click on certificates to sort films in order of certificate ...
http://www.artesea.co.uk/nowtv/movies.php
any films you then want to find out about you can click on them to be taken to the NOW TV website listing. From here you can add to your watchlist to watch on your devices later if you wish.
It's not ideal but it's the best you can do for now.
