What is a right way to send files from tablet?

See more:

TabletPC

Windows

WCF

We have native (WPF) application on tablet with Windows 8.

Tablet's user can click on Send button and it will send to server XML (or object with data) and few files: pictures or video (from 0 to many).

Questions:
1. What is correct way to send structured data: XML or our type of object (we develop both client and server side). XML seems more generic. Object requires common dll for client and server, but it’s easier way. What is correct?

2. How can we send files? Streaming? Is it correct to do streaming from the tablet? We don't know if wi-fi connection is qualitative. If it interrupts, should we start whole package from start? Maybe it’s worth to send small chunks? What is right way to monitor integrity of package?

3. Is it correct to send XML and all files in one call to the server? On the server we will start working only after receiving all parts of the package.
Can we expose WCF contract like this
SendReport (string XML, List< stream>) ?

Please advise

Thanks,
Tatiana