Most parents sensibly take the back seat and encourage their offspring to lead on any conversations and questions with the occasional prompt or follow up question. A few parents completely take over and the applicant remains utterly silent - which leaves me wondering how they're going to cope with the transition to higher education
This.
If you do go to an initial Open Day, and you are at a stall or at a Departmental presentation, or have the opportunity in some way to talk to a lecturer or student, pleeeeeease step back, allow your DC to speak, and don't keep butting in.
It is really disconcerting to have a conversation with an interesting potential applicant, and to have to constantly answer parents' questions. If your DC is shy, rehearse with them before what they might ask. BUt please don't ask it for them.
Seek out the specific events put on for parents.
The other thing is, if you do make it a "family day out' - be prepared - and maybe even OFFER! - for potential applicants to be prioritised in terms of entrance to informational lectures etc. Don't be that parent/family who insist on accompanying your potential applicant into everything, thus taking up space meant for other potential applicants. I've seen some pretty entitled behaviour from parents over 20 years of Open Days - meaning we've had to ask parents to leave, so that the actual possible applicants can be accommodated in our lecture or talk.
If it's an "Offer Holder Day" then I think it's better you don't attend. If you're driving your DC there, do something else for the day - there are often good suggestions on the university's website re local attractions etc. A lot of the activities on an Offer Holder Day are directly related to the discipline, the course of study - we do a kind of taster day to give the applicant a sense of what they'll be doing if they come to us.