IT's not just tacky, it's not done. I've never seen a wedding expert/source say that guests are in charge of their own parking fees. That is something that traditionally the groom and/or bride's family picks up the cost for. So you'll have to scrimp and save and cut costs elsewhere and take responsibility. It was after all, not the guests fault that you decided to expand your guest list and thus your overall costs? So should it be up to them to foot the bill for more guests? No. If you look at it that way, you will understand that it is just completely unacceptable- not just a bit tacky . Example: I want a fancier/bigger wedding, so if I charge the guests more for booze at the cash bar, then I can take care of some of the extra wedding costs? Tacky? Yes. Ignorant? Yes. Totally unacceptable? Yes. Basically it's the same scenario even if you don't see it that way. I want a bigger wedding so I will charge my guests parking fees.
Not giving you a hard time, just a reality check- twisting it around to a different perspective so you understand what you would be asking guests to do.
Also taking responsibility since you were aware of this fee when you booked the hall. And could have said no and found another venue. Even if you didn't know, you still can't expect guests to pay for that. Buyer beware first and foremost in signing contracts with vendors - it is your responsibility as a customer to find out every little bitty detail in the contract, what is included, what is not. It is after all your money you are spending ,and I would think also your desire to know these things. And even if you hadn't known, you still can't expect guests to pay. They are going to a wedding as invitees, not to a night club that has a cover charge.
I would absolutely not even spread the word about the parking fee, as the people who decide not to go as a result will be disgusted, and the people who do end up going will be grumbling about this long after the wedding is done about how they had to pay for parking. Do you really want people to leave your party with a bad taste in their mouth?
So sorry to say, suck it up and find the money from somewhere to pay for it yourselves.
common sense/been to many weddings/and just basically common knowledge not to invite people to a party and then tell them they have to pay to get in/theknot.com