I'm a little confused on how the alternate drop saves money. I can see where it would be less expensive than having guests order at the dinner (you'd have to have enough to cover everyone wanting the same meal, for example). But, I don't see how it saves money over having guests choose their preference in advance. Unless the point is to have one good meal (aka expensive) and one lesser one? That seems ridiculously rude, why not just have two middle-ground meals?
I agree the OP situation sounds like very poorly thought out planning. I don't think a BBQ plate and quiche are remotely comparable, and I'd be sorely disappointed if I had been stuck with the quiche. And I'm not even an older Australian man.. can't imagine what the planners were thinking offering a vegetarian quiche at all.
To the bolded above, yeah. I get wanting to save money to stay within budget. And I also get not giving people a choice, as in, everyone gets chicken. But what I can't wrap my mind around is having two different meals with no choice as to which one you end up with. And whether you can swap or not totally depends on the luck of the draw (other people at your table and their preferences) at best, or at worst, as in the case of the OP's father's dinner, whether you were among the first tables to be served or the last.
In addition, I don't think anyone mentioned this before, but swapping plates around the table strikes me as rather, well, icky. I don't mind swapping with my husband or kids, but but swapping with a stranger who happens to be sitting across the table from me is just weird.