Due to the horrible history connected to coloring chicks for Easter, and the neglect the chicks generally suffered after, very few people approve of doing this anymore even if the dying methods you use are safe. DO NOT wet or spray the chicks. That will chill them.
Do your nieces and nephews live where they can raise the chicks appropriately, or were you going to take them back home with you? Tiny chicks make very poor pets for kids; they are delicate, and chill easily. Being toted around and squeezed by kids in the midst of a boisterous Easter celebration is generally not ideal.
I'm sorry if I'm coming across as too opinionated, but I just think it's a bad idea. What about stuffed animals? They make all colors of stuffed animal chicks for Easter, and kids can take them to bed with them!