Dentist mentioned possibility of using both an anti-anxiety med (valium, xanax, etc.) and nitrous for wisdom teeth appt. is that safe to do? what would most likely side effects be?

Yes: Tiredness is the most likely SE, possible to get some disinhibition

Meds: This is not an unusual drug menu. Please follow your specialist Oral Surgeon's advice to the letter. Taken as directed this is a very safe mix. Avoid alcohol for a couple of weeks. DO NOT SMOKE ANYTHING. Make sure your mouth is scrupulously clean before going into surgery. You are having an operation, and will be sore/groggy for a few days. Don't drive or handle machinery.