The draft below is quite rough, but you can get a general idea for where I'm headed with it.
The card begins with a circle. You can see concentric circles die cut in the front, creating more circles.
The first circle swings away to reveal another message for the receiver.
The second panel swings away as well to show the last message, with the details about the party and rsvp information.
This was mocked up quite quickly (once I had a concept, it came together like lightning) and, in order to get some pix to show my potential customer, I had my neighbor girl stand in as an unpaid hand model (hence the dirty fingernails). Also, I really need to work on finalizing the artwork -- I'm not at all happy with the initial panel...
If the mom likes this concept (keep your fingers crossed!), then I'll finalize it for her and, later on will post a genericized version on my etsy site for sale. The idea of polka dots for a first birthday party is totally darling and opens up lots of fun ideas for the cake, decorations and games (if some of the guests are big enough to enjoy them).