Fundraisers planned with no notice are the parent group at work. School personnel don't run these things. As far as field trip notices, the trip has probably been publicized in newsletters and web sites for awhile. If you send them home with too much time, they never come back.
My experience, now that I am in another field, is that most people have no organizational or time management skills. One of the people I graduated with was already fired for not doing her paperwork in a timely manner.