I have read over a good chunk of the threads for tastings but none seem to work well in my situation

I am just starting out and bake only to order so I do not have cupcakes or extras in my freezer. I taste tested my items and the cakes/cupcakes start to taste odd after 2 weeks. I also do very few tastings per year as I only do them on request.

I have a bride who has requested one and I am trying to think of the best way to do this. I mainly do cupcake towers and small mini tiered wedding cakes to top these towers.

My thought was to offer only chocolate and vanilla cupcakes with vanilla icing on top. Maybe even mix the 2 and create a marble so 3 flavors. But that only leaves me with 1 buttercream, my vanilla, which is my most popular.

I charge $25 that gets applied only for orders over $400 - orders between $200 - $399 can pay for a tasting but it does not get applied to the booking.

So does this sound right? Any suggestions on how to make this better or improve it?

What you have written sounds very reasonable price-wise. Frozen cupcakes will take on the funny taste if they are put in a frostless freezer like the kind attached to a fridge. If they are kept in a stand alone freezer things can keep much longer. I would suggest along with your vanilla to give the illusion of more choices by adding different extracts to your divided vanilla batter: add lemon extract and maybe a bit of zest = lemon cake; almond extract = almond cake; creme bouquet = wedding cake flavor. That would double your flavors without much extra work.  Since most wedding cakes are white you could do the same with your vanilla frosting base and add some of the extracts. 

Good question. I offer 6 cupcakes per flavor (half a recipe, that's doable) and different frostings. Well I do ganache and everything else has a smbc base (just flavor it) so it's easy and I charge extra for alcohol and curds. 6 ccs is not too much or too little. If they come with family everyone can have one of each per flavor and if they are alone they can take 4 home per flavor. So unless they order 10 different flavors they won't have too much "leftovers".