Per the regulation, MDD products that were on the market prior to the MDD cert expiry date can be sold until 27 May 2025. This is the only requirement in the regulation. I do think it would be a smart idea to keep on hand the documentation that shows these products were lawfully approved under MDD and on the market prior to the expiry date just in case you get questioned later on.
Whether your customers would have a problem with receiving MDD product is a different question.
Is there any actual difference in the product? I imagine there may have been label updates to comply with MDR - will customers notice/care about the differences? If any information was changed (eg, authorized rep, NB, etc) will the customer be able to find the info they need? Does the labeling have all languages required for the region you are distributing in? Again I don't think this is a strict requirement of the regulation, just a "CYA" measure that you may want to think through. As a distributor these considerations may not even be an issue for you. Just something to think about....
Also note that if you distribute to any other distributors, they may have concerns about receiving MDD product, especially if it is crossing country lines.