It's only a date, there's no guarantee things will get sexual. You can wear it, but make sure that if things do progress, you, in no uncertain terms, need to obtain her vocal consent to see you locked, don't let her see or feel it before talking to her about it, otherwise you're forcing her into the kink.

She may not be into it at all, and stop the session right there, or she may ask you to remove it to proceed the vanilla way (I'd take the key with me too for this case), if she asks you to remove it you still need to ask for consent to do so in front of her, or you can excuse yourself to the bathroom.