For activities, I always suggest decorating cookies. Another activity for them is to distribute blank index cards, cut to Pokemon card size, and have the kids draw their OWN Pokemon. They can invent the names, their looks and what special powers they have, and create an entire habitat. Then they could trade with each other. Office supply stores sell business-card sized magnets that have adhesive on one side for the child's own design.
Most kids enjoy face painting.
If you have illustrations of various Pokemon, you could let the guests pick a character to be. I can't think of an easier cake than a Pokeball, decorated with red, black and white icing. Use a high-quality food coloring paste or gel in a bold yellow for the frosting. We appreciate your feedback .