Be sure to chill your champagne before you add it to the frozen fruit. If the champagne is warm the ice will melt too quickly.
Why not try this champagne slushie with different berries? Frozen blueberries, blackberries and raspberries will all work well.
If you prefer your slushies thicker, once the frozen strawberries are blended, you can add in ice cubes and blend until you get your preferred thickness.