Here is our simplest sugar skull tracing page - very like the skeleton masks worn during the Day of the Dead parades. It's simple outlines leave plenty of space for embellishments or could be suitable for younger children.
Trace over the dotted lines to make a pretty marigold - or just a generic flower - read to be coloured in. Marigolds are used for decoration in Mexico's Day of the Dead festival.
This lovely, decorated owl face was originally designed for Day of the Dead, but I think the kids would enjoy tracing over the dotted lines and colouring in some of the details at any time of year.