To the OP, yes, as others who agree have already stated, on these specific cakes, it is YOUR job to describe the cake, not, have a "Let the buyer beware" cake policy.
Sorry, but again, a premium price calls for premium quality. And when I referred to "premium", I meant a cake decorator who calls themselves a professional and charges accordingly. Walmart can add a margarita mix.
When someone asks for these flavors, you had better be sure of what the customer wants of be prepared to refund. These cakes require detailed information. And yes, you can be catty and reason why by posting that you do not describe your chocolate, but in some cases, this is also needed. Do you think I would sell my $89.00 German Chocolate Cake over my $50.00 traditional without explanation? No, but I do describe, and I have only sold one traditional. The other is a best-seller.
If you are going to make a cake based on a drink, you should specify if it is a mix or the real deal. And by the way, I have never made a margarita with a mix, and maybe you don't know this, but many places do not use mixes. They are the low price, bottom quality margaritas. They are nasty in a drink and I can't imagine adding it to a cake.
And you, yourself mentioned variations and that people ask for them. But with no instructions, a margarita will come to you with salt.
I don't drink a drop, but I have bartended at a casino at the high roller bar, so I have extensive experience with how people ask for their drinks. We didn't have a mix anywhere in site.
So to all but the OP, be sure to detail these specialty cakes not only on your site, including the process and the ingredients, reiterate this when talking to your client. Anyone interested can look on my site and read my descriptions. On specialty cakes, you want to allow them to taste the cake mentally and you need to deliver that exact cake. The accurate description will keep you from surprising the customer with something they don't like and will insure that you don't have an unhappy customer asking for a refund.
And no, I do not take the opposing side just for the fun of it. Other people besides the OP read these threads and this one, since I sell so many alcoholic cakes, is one that I happen to have experience. I have also shared the use of alcohol in cakes numerous times on CC and in multitudes of PM's.