If you want to give family members a sense of participation on Seder night, it is important to involve everybody already at the preparatory stage. Youngsters who prepare in advance will feel a part of the Seder, and they will look forward to it.
The end of the seder is a transitional period. We leave the intense study of y’tzi’at Mitzrayim behind and move on to the time where it will again just be mentioned. Perhaps the taste that lingers is a message. Take some of the intensity and the depth of the seder experience and have it linger on as long as it can.