I know someone who is very allergic to soy and wheat and dairy. "Basil pesto entree" sounds like it might have wheat in it, possibly a pasta dish, so he'd steer clear of that, not knowing it has tofu, which he also can't eat.
If you are going to serve vegan food and you know some of your guests won't be happy, you have two choices. Accept that they will be unhappy OR change your menu.
If you do the menu response cards, it's best to be honest about what the food is. But they do open you up to weeks of complaints about the menu.
Could the caterers do a buffet? That way, you get the food you want, no one has to be notified ahead of time, and the majority of the complainers will have complained themselves out by the time you are back from your honeymoon.
There's nothing rude about serving a vegan meal. Nor do I think you have announce your food choices before the wedding. But you can't hide the ingredients from people.
And if you do depart from the "average" US diet, then I think, sadly, that you need to expect comments. Best to figure out how to deal with them ahead of time.