Meclizine is the active ingredient in some of the over the counter preparations of Dramamine (see Dramamine Lo-Dose) where Dimenhydrinate is active ingredient of the original formulation of Dramamine. However, Diphenhydramine (which is one of the active ingredients in Dimenhydrinate) is the active ingredient in Benadryl, which is an antihistamine (and is used in some sleep-aid medications, because it causes drowsiness - see Tylenol PM).
Both Diphenhydramine and Dimenhydrinate may cause drowsiness, so definitely take it the day BEFORE your mix session to see how your body will react, because you could find yourself snoring and drooling on your keyboard in no time.
I have to take Meclizine from time to time for recurring bouts of
BPPV (which is the worst fucking thing ever), and it has no effect on me at all. Meaning, medications react to different people in different ways, so trial yourself on Meclizine (or its derivatives) before you use it in practice. It may have a huge effect, or no effect at all.