Hi S.,
I just wanted to write and say I have experienced similar situations. I have a sister with 8 children. My house is small and is limited in how many we can accomodate. If I invite my sister then we really do not invite many other children. Like you, a lot of planning goes into these parties and the birthday child picks out a theme, games, helps with goody bags etc. They are very excited about their birthday.
When the time for the guests to arrive comes and goes and no one shows up it is heartbreaking. My sister has left me holding the (goody) bag more than once. I will say, I have simply stopped inviting her.
It is best to try to have an upbeat attitude about it because children really pick up on our emotions. These days so many people invite the entire class that maybe they thought their prescence wouldn't be missed. In the future, if you choose to invite these same people I would follow up with a phone call confirming the date and explaining you just don't want a similar situation to occur.
Shame on those parents who do RSVP and then just don't show. How can you teach your children manners if you have none yourself!
J. L.