Adding extra info the the entire order?

Hey, I’m building a site for a shop and they want to be able to have a section where people can choose a time period for when they want to pick up their purchase from the shop. The shop-owners want to limit the choice to 3 different options.

Is there any simple way of adding a selection like this and have it apply to the entire order?

If not, is there some sort of way to make a product variation that applies to an entire order, or some way I can make sure that all the orders use the same type of variation if I went in that direction?

And if that is too complicated is there a way to make the choice that buyers pick from the variation to show up more prominently on the sales reciept so it’s easy for this business to figure out when they need orders to be ready by?

I would prefer a solution that would require the least amount of edits to PHP, or if there is any real solution at all without a complete rewrite of the code. However I am familiar enough with PHP to make simple edits here and there.