When my husband was prescribed Aricept (aka Donepezil) we specifically asked the consultant about whether he could have alcohol too and she said it would be ok, within moderation.
Hubby does not drink to excess. We share a bottle of wine when we go out for a family meal (approx 4 times per year) - then he'll have two or three units on special occasions such as Christmas/New Year or our annual family BBQ. Other than that he'll just have the occasional drink at home a couple of times per month - usually when we are watching a film.
If ever he reaches a stage where he starts to lose track of how much he has had to drink and it becomes a problem, I would just switch to the alcohol free brands as already mentioned or water down the normal ones and hope he doesn't notice