Your sentence is correct as originally stated. You can also use "seafoods" and "meats," which are acceptable plurals of seafood and meat -- although less common. Some might argue that this produces a slight change in nuance, such that "meats" implies "types of meat" and "seafoods" implies "types of seafood." However, even if the case, this distinction doesn't seem substantive in your particular context. I would use what you think sounds better.
The "while" is not necessary and tends to imply you'll say something contradictory in the latter part of your sentence.
In terms of challenges to the sentence, most of it I think has to do with word choice.
"Mixing and matching" isn't something that we often apply to ingredients. It's a bit odd to think about what matching different meats means. In culinary writing, there's often a statement about "pairing" food items, e.g., pairing a steak with a cabernet sauvignon. However, this is usually reserved for pairing completed dishes and not ingredients. A simpler phrase, such as "Mixing different kinds of vegetables, ..." or perhaps, better for a cooking context "Combining different kinds..." Since mixing has a particular meaning when we're talking about recipes and we'd actually prefer a more general meaning.
"Newly added dishes" is a bit odd sounding, but it may depend upon the context. By itself, I ask the question "added to what?" But if this is part of a discussion on, say, creating a recipe book, this might be understood.
"This and that" is also unclear. This and that is often used to describe a collection of unrelated items and while certainly there are vegetables, meats, and seafoods -- they still seem pretty coherent as a set of items. I recognize that this and that refers to dishes, but, once again, it's not apparent to me that they're that dissimilar. I'm not exactly sure what the original author was trying to convey. However, if you can make it more precise, that would be greatly beneficial (e.g., "... are very distinct.").
