The public comment period for the change to require (rather than request) all Social Media "handles", emails, and telephone numbers ends 10 Feb 2026, and will be followed by a formal review. If the changes do go forward they may be implemented as early as March but no target date beyond "Spring 2026" has been publicly announced. So there is still time to apply for the ESTA - it's valid for two years provided your passport doesn't expire in the meantime. If you ARE turned down for the ESTA, nothing happens except that you'll have to apply for a visa if you still want to go. (Of course, don't book anything else until you have the ESTA or Visa approval).
ESTA and Visa vetting in general is intentionally opaque to avoid helping actual bad actors gain information to bypass the checks. But officially, the purpose of these proposed changes is to better identify risks to national security or public safety, to flag individuals who have committed crimes or have ties to terrorist groups, and to flag people who might have misrepresented themselves on the ESTA itself and/or are ineligible for the VWP, etc. - for example, an ESTA applicant posting about staying the the USA for longer than the Visa Waiver allows, or about "moving to the USA".
Based on what IS in the public domain, I'd say that deleting individual SM posts or closing accounts right before you apply (you still have to list any accounts that have been active in the last five years) could raise suspicions. And of course don't suddenly start posting pro-Trump stuff if you've been critical or indifferent in the past - they're looking for inconsistencies, clues that you might be hiding something or misrepresenting yourself. Otherwise, liking a couple of random posts poking fun at Trump is likely not an issue, liking even a few posts calling for physical violence against the President or the overthrow of the government absolutely could raise a red flag, in which case your application would be reviewed by a human agent (initial checks are AI).
If your son is likely to act in a way that could be interpreted as a security threat at Arrivals, I'd probably not travel with him internationally. But if you decide to go and are still worried you also might ask local friends - or perhaps someone from the uni, if you've been invited in an official capacity - to meet you at the airport or be on call in case of difficulties.