I had to cover this topic several times in my newsletters too. We tried to explain 1) why Florida; 2) things to do besides theme parks; 3) cost expectations depending on if you were making it a vacation, etc. I can't remember if I send you my newsletters a while back or not (I think so, but maybe it was the scavenger hunt). If you want to see how I covered these topics let me know and I can email them over

Also, check to see if a lot of family are flying you can sometimes set up group rates through the airlines. I did this with my family from Michigan for rates on Airtran.
In the end, anyone who doesn't come you can't let it bother you. As my one aunt told me when I was upset about some relatives not coming, they are the ones that are missing out on a once in a lifetime experience.