Skating on any surface, real ice or synthetic ice, will dull the edges over time. Since most synthetic ice rinks are small, kids tend to use their edges more than they normally do on large real ice surfaces. With the amount of skating they do on synthetic ice compared to the amount of time standing around on real ice, you will find that the skates will need to be sharpened more often. Some synthetic ice surfaces have more friction that others. This will affect the rate at which the edges become dull. Synthetic ice rink owners and users are switching to practice skates to reduce the overall wear on game-ready skates.
The real concern about blades should start with who is maintaining your blades. See this blog post that addresses this concern.