sorry it wasn't much of a reply but there really isn't a product that prevents cracks, as the bad as that may sound those products that are being advertised such as the Armor all and even Meguires Dash board wipes or shine are not worth using because the end result is cracks, I know this because I used those products on my Ford T-Bird and after some time a huge crack appeared right in the middle of the dash board, that's why since then I never touched any dash board products, I only wipe down my dashboard and just use the window cover to prevent the sun from coming into my car.
If I'm not mistaken either you have tint on your ride as well right? You shouldn't worry much, like I said those products contain UV 'checmicals' that will do harm to your dash even when it looks all pretty that prettyness goes away and when it does...that's when you wanna wish you never used them.