Not being negative here, being constructively critical (I think).
1 - No, the smile looks kind of strained as in "Is this how you want me to smile?". To *me* in imparts "uneasiness".
2 - A nice shot and she does look like she knows what she's doing (from myself mentally recalling images of other people holding and playing violins). To me, though, her gaze leads my eyes away from the image and off the canvas....to whatever it is that she's looking at (which I can't see). I think she's probably looking at someone directing her, but I'm no violinist (or musician of any instrument) so without knowing about and the time to think about her prior study and current concentration it leaves me with a sense of "disconnect"...does that make sense? Possibly her eyes downcast in concentration (as shown in the photo of yourself) would work better? I would have liked to see a touch less room on the left and more room on the right beyond the scroll...(I googled the name for that part<g>.
3 - A happy child holding a prop. Probably the best shot that will "appeal to the masses".
Now, it depends on your clientele. If they are in your circle of friends who are aware of your daughter's study of the violin then either of the latter two would work well...I'd give the #3 a bit of an advantage, though. With either of those two a very short lead-in by you about your daughter studying the violin could transition ignorant clients (like me ) into understanding and appreciating the image.
Since you're wanting to promote canvas I would think the wood grain of the violin would be at home on canvas...thinking back to old canvas paintings of musicians I seem to recall the wood is prominent in those images so keeping the violin in the image "connects" with the idea of canvas.
Your daughter is precious, a real beauty. She is in between the age of my middle and youngest granddaughters. The kids these days are sponges that absorb everything around them and catch on to things in a dramatic way. With the concentration I see in her face I think you are igniting a passion that will live with her throughout her life. Well done!
ETA: I apologize for anything that might seem negative about your daughter. I'm only trying to be constructive in the above and give you my honest thoughts. Best wishes.