I don't know about the children's chewable aspirin, but I am aware that Vitamin C (ascorbic acid) can be added to doughs, and have done this with bread doughs, but not pizza dough. Many commercial flours already come with some ascorbic acid as a dough conditioner (General Mills has several flour brands with it) to make the dough more manageable and help the yeast work better (longer and faster) and produce a higher rise. It is also quite common to find a small amount of ascorbic acid in instant dry yeasts, to produce an acidic environment for the yeast, which is apparently a desirable thing. I have also seen commercial dough enhancer/relaxer blends that include ascorbic acid, I suspect for pretty much the same reasons mentioned above.
In my case, I already had some Vitamin C in powder form and I used a pinch of it in the bread doughs (sourdough). Before that, I just pulverized an ordinary Vitamin C tablet. I can't say that I noticed any difference in the finished bread loaves. You might want to try it, perhaps in a munga cake (did I get that right?