We live in a very small isolated community. We also have a small school (14 children): I am the director. I look for opportunities for the children to participate in Tzedakah in the community so that they will feel they have common goals. There is a large event that is sponsored across the country called Cropwalk to help raise money for food for people throughout the world. We have participated in this event in the past as a school: children can get people to sponsor them as individuals or as part of a team. This year, cropwalk is on May 1, the 8th day Pesach. The event allows for advance registration over the web so that all our walkers can register before Pesach begins. It also allows people to donate money on behalf of our team or its members over the web. So we can arrange it so that there is no writing or other activity to do for the Cropwalk on May 1 except to walk. The cropwalk starts around 1 pm so it doesn’t conflict with services. I can arrange to have kosher-lepesach snacks available at a midway point. Can we do it? Can we do it even if we know that some parents may drive their children to the start point? (Am I responsible in suggesting this event for decisions the parents may make regarding driving?)
This is a very heavy question which should be answered by a rabbi that has a closer relationship with this specific community. In general we can't invite people to an event – even a good one – if it will force them to break Shabbat or Yom Tov; i.e. we don't invite a Jew for a bar mitzvah on Shabbat (knowing he will drive) if he can only get there by car. If the person can get there without breaking Shabbat but we know he will – here there are some authorities that for a good cause that will bring Jews toward Yidishkite will permit such an invitation since he is not breaking Shabbat because of our invitation. Is your case the same? I can't tell from so far away but I have a feeling it isn't. I feel you will gain more if you will announce this year that we don't participate that important walk since it clashes with 8th day Pesach.