The caveats regarding model releases and proprty releases are contained in the paragraphs regarding 'commercial' and 'international' useage.
Most stock agencies sell worldwide and therefore require releases for just about everything to cover themselves.
For a personal portfolio website based in the UK or EU, you wouldn't need them, even though those images could get you future commissions.
While they're not legal requirements in the EU, it's a good practice to have them in a CYA scenario.
With regard to the OPs particular shoot - the parents presumably consented for the camera-club to photograph them?
Unless they specifically demanded that they not be published, I doubt there's anything legally they could do to prevent the images being uploaded and shared online.
I do think whoever organised the shoot might have been a trifle naiive in this instance if there was no paperwork available to be signed by all present - maybe a lesson-learned for future events such as this?