Will the special requests my customers make, like a late check in or two rooms next to each other, actually reach the hotel?

Yes, your portal can collect special requests when the booking is made and pass them on with the reservation, but whether the hotel acts on them is never guaranteed. This is the one part of hotel booking that stays outside anyone's control, so it is worth understanding before you promise anything to a customer.

On the booking page your staff or your customer can usually add requests, either as free text or as set choices such as a twin bed instead of a double, a non smoking room, a high floor, rooms close together, or an expected late arrival. Those details travel with the booking to the supplier, and from the supplier to the hotel. How far they get depends on the supplier you are connected to. Some send the notes straight through and print them on the voucher, some only accept a short amount of text, and some do not carry requests at all on certain rate types. If you work with several hotel suppliers, you may find one handles this better than another.

It also helps to know which things are really a request and which are part of the booking. Bed type, adjoining rooms, early check in and room location are almost always requests that the hotel decides on the day, based on what is free when your customer walks in. An expected late arrival is still well worth sending, because hotels can release a room if nobody turns up and no arrival time was given. For anything a customer truly depends on, such as a wheelchair accessible room, a cot or a connecting door for young children, treat it as something to confirm directly with the hotel rather than leave as a note.

Before you go live, make a test booking through each of your hotel suppliers and see exactly where your request text appears on the confirmation and the voucher, then word your own booking page so customers know a request is not a promise.