Banks have the option according to UCC to pay post/stale dated checks. But do we have any obligations to the person presenting the check for payment?

You only have obligations to your customer. They have "loaned" you their $ with the understanding that you will pay it out based on their instructions (and subject to certain standards). The authority to pay stale or post dated checks was created to "authorize" bulk filing, not to override ordinary care. If you are presented either at the teller window, you have every right to refuse to cash the check.

The irony in Al's response, with which I totally concur, is that the payee who takes the trouble to present the check at the drawee bank will (likely) be rejected due to a stale or post-date. But the payee who simply deposits the check will most likely have a happier result.