Re missed offers - here's my tuppence based on DDs' cohorts over past couple of years, at both places...
Oxford - we know of a small handful who were still offered with a narrow miss (I'm talking 1 UMS off in an unrelated subject i.e. Maths for a Humanities degree) - however, and here's the biggie, in each case there were other mitigating circumstances, in one instance prolonged illness during Yr 13. I can immediately think of many more who 'lost' the place with a combination of say A*, A, B, for an AAA course.
Cambridge most certainly seems to over-offer more and use A levels as a final hurdle (and as for the poor Mathmos with STEP..). Factor in as well a noticeable anecdotal increase in higher than typical offers last year - ie AAA for Humanities vs A*AA etc and the use of adjustment for the first time, definitely less wriggle room for missed grades & placement through Summer Pool. I'm struggling to think of anyone who missed such an offer, who still achieved the typical offer, being accepted. I am equally sure, however, they take a close look at contextual information in making these decisions, so it's impossible to give a hard and fast rule.
The other thing to bear in mind - and I've seen this first hand with one taking the 'old' modular A levels and the other taking all linear - it's so much harder to predict how grades will pan out - there were some real surprises in 2019 (especially amongst Humanities results) - students performing (in schools' eyes) at A level, coming out with As & Bs - and vice versa. And of course the percentage of As attained nationally dropped for the first time in Lord knows how many years. All these factors mean that the Unis have to recalibrate their expectations on results day & it may well work slightly differently across subjects.
Sorry, a lengthy response to essentially say that an offer should absolutely be celebrated for the success it is, in its own right (we did in this house). With a strong caveat that no matter how proud we were of them, there was more water to go under the bridge and all we could ask is that they did their best come exams. No pressure or further expectation. We also invested a lot of time in ensuring that the Insurance was a real alternative and somewhere to be excited about - I've no doubt that if either had gone to their Insurances, they'd have flourished and had a great time.
I have everything firmly crossed for all of you and your DCs - best of luck!