One craft I remember doing at their ages was decorating easter eggs. You can take foam eggs any size and get string/colored paper and using craft glue decorate the egg. You need to cover the entire egg, so just use small pieces of the paper. Kids love this because it is a little messy. In the end it looks like a collage all different types of paper but still like an easter egg due to the colors you use. After it is dry you the adult can then spray schalak (sp?) or using a decopage type paste over the paper to finish the eggs. You can then hide these or they can take them home for next years decoration.
Another is have them use pens to decorate wooden eggs. THen you can put the date and their age on them. DO this every year and you not only have a tradition but you can see how their art skills change.
Have fun.