What are they going to pair it with?
This will be paired with the salad course.
I wonder about reserving the puree to be served with the beer instead? I envision champagne flutes with a teaspoon or so of raspberry puree at the bottom and a bright golden ale on top, maybe with a Belgian yeast?
I like this idea! Keep in mind that if you add puree at serving, its best when made fresh.
Served at/near the beginning of dinner, you'll want to keep the beer light and crisp. If you don't want to mess with adding it in the glass, you could:
start with a traditional Belgian blond recipe,
ferment lower in the temp range (65F or so),
add the puree at the end of primary to ferment out any residual sugar,
carbonate on the high side, around 2.8 volumes (enhances aroma, scrubs palate).