I made Will a little Flash birthday card. This one is called Will and Mater. A normal card would probably have been faster, but making the birthday greeting do something is more fun.
The browser page loads a compiled WillAndMater.swf movie. The interactive content is inside Flash, not in a JavaScript game loop on the surrounding page. The exported movie includes Flash display and event code, while the HTML mostly takes care of embedding it at the right size.
I like having a few different ways to make these family projects. Sometimes a page full of layered pictures is the right fit; sometimes putting the presentation together in Flash makes more sense. The important part is getting to make something specifically for a nephew instead of picking another generic birthday greeting. Happy birthday, Will!