I don’t think it’s necessarily an ‘Olympic’ moment, it’s more that missing a week of training for a family trip and a party will set the child back for near-term goals - club competitions, the opportunity to get PBs, losing fitness etc. A week of missed training probably takes about a month to recover.
So if this choice is likely to mean your child misses out on a medal, or it impacts their short-term goals (keeping squad place etc), then that is more of a consideration than whether this choice is going to affect their long-term progression.
I expect this is gymnastics due to your references to lockdown zoom training - but our swimming club absolutely selects ‘elite’ swimmers at 7/8 and expects 100% commitment. Older children can still join (whereas with gym it’s hard) but swimmers are expected to make the same sacrifices.
It all depends on your child, their enjoyment of the sport, their other interests and whether they understand what a week long break will mean for their near term goals.
My dd is 12, she loves swimming, she swims for a great club but is relatively slow compared to other squad members. She never misses training, she loves getting PBs, she loves standing on the blocks in front of spectators and trying to beat quite a select group of swimmers who are a similar speed. She trains 9 hours a week and I never have to tell her to get ready - she sits of the sofa wearing her costume an hour before we leave the house ! I know that if she misses training for a week before a gala her times would be slower - she knows it too, it would be her choice.
My job as a parent is to enable her ambitions and support her - whether she’s first or last. And it’s to give her a range of activities to try out to see where her passion lies. My 16 and 15 year old ds/dd are downhill mountain bikers and race regional and national races - my youngest loves tennis. But I could never ever force them to do their sports - they would be miserable.
It’s not all about winning medals and getting to the Olympics, it’s all about building confidence and letting them take it as far as they want. I do think it’s your child’s choice - but as another poster said, they have to know what missed sessions means (in terms of near-term goals), and decide from there.