Use a spoon to coat both sides of the matzoh pieces with the chocolate. Drizzle the sprinkles on top. Let the coated matzah pieces cool on the wax paper until the chocolate is completely firm, about 2 hours. I don't see anything in vanilla extract or imitation vanilla extract that would be unkosher for Pesach. Regular real vanilla extract contains alcohol, which may be derived from a prohibited grain or corn.
Some brands also contain corn syrup.
If the alcohol is from prohibited grain, the vanilla extract is considered to be hametz. While the exact kitniyot custom may vary slightly according to different authorities, most Passover products in this country use the strictest Ashkenazic interpretations. It contains no forbidden alcohol or corn syrup. I mix the berries and syrup with the fresh fruit and sometimes toss in broken walnuts. The recipe is, of course, very flexible.