Yes you should be able to use your TS credits at a CS place. (just a side note, if you are paying for the plan you should down grade as is isn't a good way to spend your credit. If you got free dining then it isn't so bad, but you did pay to upgrade...)
Now your credits are based on nights at the resort, so everyone will have 4 nights of credits. (hopefully you know that already)
They can be used whenever you wish during your trip.
CRT is a 2 TS credit meal, so it isn't a big of deal for you, but your friends will take half their credits to do this meal. Or are they paying OOP?
(it might be worth it for them to pay OOP for this meal) As they will have to pay for 2 other meals in order to use those credits for this one.
Without knowing you and your party's tastes it is hard to recommend. But I can tell you some of our favorites.
Crystal Palace in MK is my fav. It is a character buffet with Pooh and friends. I love the food, the atmosphere and the fact it is all within MK. Don't have to go anywhere for this meal.
Ohana is another favorite. It is an all you can eat family style meal. They only serve the all you can eat, there is no menu to choose from. But the food is fantastic. Ohana is at the Poly.
Whispering Canyon Cafe at the WL is my husband's favorite. He loves the all you can eat bbq skillet and the antics played by the servers. He aggravates them and they him back...he is such a kid.
Kids love this place as it is loud, the antics and it is rustic, cowboy themed, very cute. I too like it, but for the ribeye I get there. I could do without the antics. LOL
Good luck with your trip and have fun!!!