Don't forget to think about future growth, too. 50 people can quickly grow to 100, and then its not uncommon for people to have 3-5 wifi devices on their person (cell phones, smartwatch, laptop, barcode scanner, etc). Plus IoT, VOIP, etc. So it's not unreasonable to think you might have 500 devices on this network at some point.

Don't forget about outside, too. Not sure about your specific warehouse but think about people potentially needing to move goods outside.

AC-PROs are a decent baseline. HD might not be necessary in a warehouse environment. You can also mix and match, so it might make sense to put an HD unit on one end, where you expect staff to be more of the time (eg. near a lunchroom/office area).

But the nice thing overall with UBNT is the APs are cheaper so you can be more liberal with placement. $175 for an AC-Pro is a far stretch from like $600 for a competing AP.