Bulk orders that ship one at a time when the customer is ready

Hello, I have a small shop I’m working on that carries handcrafted gifts that we make. I have a question about a program we’re trying to implement for this shop.

Some of our items are engravable and we want to offer a program to real estate agents, home builders, and other companies that give gifts to clients. We will allow them to buy a bundled order of 5 or 10 charcuterie boards or cutting boards in advance, but not actually have them engraved or shipped until they need the gift for a client. I can do this all manually using a spreadsheet, but I was wondering if there is an app out there that might handle something like this where they could log into their account and see that they bought 5, and have 3 left (ideally they’d also see their previous orders but I don’t want to get greedy. Does anyone know if there are any apps out there like that? or something similar to it? Any ideas? Thank you!