Hi Maythe!
I was excited to see your question because I'm a Walt Disney World shopaholic and I make a living by consulting with companies on sales tax issues. (No joke!!)
To answer your first question, you can definitely ship your souvenirs (or other items) back to your home even if you don't elect to do it at the time of purchase. The easiest way to do this is to go to one of the
business centers at either Disney's Yacht/Beach Club Resorts, Disney's Boardwalk Inn, Disney's Contemporary Resort, Disney's Coronado Springs Resort, or Disney's Grand Floridian Resort & Spa.
Now, on to the juicy stuff...your sales tax question!
The short answer is yes - the cast members will not charge Florida sales tax if you elect to ship your purchases home at the time of purchase. If you instead take possession of your purchases and later decide to ship them back home from one of the business centers, they'll charge the sales tax.
Here's the hitch - when you go home, you may owe use taxes on any purchases that you didn't pay the Florida sales tax on. I don't want to geek out on taxes, so you should consult your tax advisor on that matter.
Here's a little tip from your buddy Derek:
While we're talking about shipping...don't forget that it may be cheaper to ship things to your hotel than it would be to haul it in extra suitcases. Instead of paying for the extra luggage for diapers and other baby supplies, we go online and ship them to our hotel so everything is waiting for us when we arrive. With the sites that offer free shipping, it's cheaper and a lot less hassle when it comes to packing.
I hope that helps! If you should have any other questions, please feel free to write back and I'll be happy to help in any way that I can.
Best regards,
Derek