There is no major problem doing extractions with a facial while on tretinoin, although the skin will be a little more sensitive during the procedure and a little slower to heal. Ideally I'd stop the tretinoin 3-5 days beforehand, and restart 3-5 days afterwards.
Many people who get facials are also on tretinoin as this medication helps loosen the plug in the pores. As long as the person performing the extractions is properly trained and aware that you are on this medication it should be safe. It's best to ask the person performing the procedure their preference. There is a slight, increased risk of skin irritation while on this medication.