Stevia (often sold as rebiana) is a natural sweetener from a plant. (But see my edit below)
It is not like saccharin (e.g. Sweet & Low), sucralose (e.g. Splenda), or aspartame (e.g. Equal). So it's not artificial. However, it is often processed with all kinds of stuff you don't want and which are terrible for you. So you have to read the label to see what else is in there, and also where stevia (or rebiana) occurs on the ingredient list - if it's the 4th or 5th ingredient after a bunch of other stuff, you have to re-think it. I get mine on line because I haven't found anything in the grocery store that isn't loaded with junk.
Same goes for things loaded with corn syrup or corn syrup solids. Plain sugar would be better.
I think it makes sense to rethink your Dr. Pepper and your KoolAid, of course, because they do build up a craving for sweetness. That makes you, and the kids, want other forms of sugar too. If they really want flavoring, can't you save their teeth and a lot of money with water and a squirt of lemon or fresh orange slice - even a few slices of cucumber sitting in a pitcher of water in the fridge change its flavor to make it seem different - although I think the idea of doing that or buying artificial flavor drops for water kind of sends the message that "water is bad". Then there's all that artificial red dye and other color dyes in there. If you read the ingredient list of the sodas, you'll be amazed.
But you're absolutely right about these artificial sweeteners causing all kinds of problems, and there is a ton of data about how the pancreas reacts to it. They've been on the market for decades (with pitiful testing), and we have a far greater obesity problem than we did before.
If you like something fizzy, why not have regular seltzer/club soda, watered down halfway with plain water, and/or with the natural flavoring added, or add a squeeze of lime, lemon or other fruit? I think you'll see a difference in everyone's health, their other food choices and your budget.
(Edited to add: stevia is the plant itself; rebiana is a derivative from it which some people question BUT it depends on how that rebiana is processed. Moreover, it is often added to things like erythritol and other lab-produced items which you may or may not want to consume). Pure stevia is a plant, just like sugar cane. And sugar cane is processed into a variety of sugar products, with white sugar being the most processed and having the most nutrients removed from the plant. There are so many forms of sugar in your store, for example: brown (light/dark), turbinado, etc.)