"On the larger issue, of getting kindergarten children to pronounce the numbers from 1 to 10. Uh, do you really need to use a computer? Running Mathematica?"
Not meaning to disregard the top part of your post, however the last two questions are important to me. I would like to get your opinion as I see that you are a well cited author of over 1100 documents on the Mathematica site.
I hope that I am interpreting your question correctly. I would say I hope a student would not need a computer to run the manipulate, and if I am under standing the way CDF's, such as those on the demonstrations project, work it could be run on a smart phone, a pad, or other such device, (w/o the player) that the student may be using while riding in the back seat of the car, or at other non-productive times.
Now if the question addresses the only necessity of the pronunciation of numerals, then I would say that it would be a good addition to a demonstration that targets an age group that are multi-sensory, but I guess not a bsolutely essential. I would also hope that such an instructional method would only be supplemental to more personal , probably tactile-engaging, methods of presenting the concept.
Reality, of 35 years teaching, says that there will be many students that will for whatever reason miss the point that numerals represent numbers, and come away with the idea that 3, whether written or spoken is two backwards c's stacked on top of each other. Given that as a foundation on which we would like to build the rest of their mathematical understanding is it any wonder that by the time that they are ready to do more complex mathematics many become discouraged?
I think that if this app can include audio, without disrupting the learning flow by showing x number of objects on the screen while speaking the number y, it would be more worthwhile to students in this age range.