The highest version of officially supported Win32 client with Micros is Windows 7, though I did successfully get it running on a Windows 8 tablet. If you really want to go that route, go Windows 7.. if you can't find one with Windows 7, make sure you have Windows 8 not Windows RT; a lot of vendors aren't differentiating clearly enough.
To check how many licenses you have, open the License Manager. The quickest way is to open the run manager (Windows Key + R) and type licmanager. You can also find it through the start menu: Start -> All Programs | MICROS Applications | Utilities | License Manager.
Once you open this, go to the POS 3700 tab. On the right hand side, you will have the list of license codes, and above that you will have three additional tabs. Click the Clients tab. While you might have more license codes than are listed, most micros installers put them all in. Check how many you have listed and compare to how many workstations you have in use... if they are all in use, you will need another code. If they aren't all in use, you can add either a CE or Win32 client without needing another code. Even if they are all in use, it is possible that you have an additional license code, but you'll need someone who has access to the Micros website to check for you. You'll have to give them your key number for that.
Let me know if you have the spare license code and I can walk you through setting it up on your tablet. As a note, for the wireless, it will be infinitely easier if the wireless is just a bridge into the MICROS network, but be careful with that. Go for something secure like WPA2 AES. Once your Micros network is in the air, you increase your chances of being breached, but with proper precautions (hidden SSID and a good password) can offset that enough to make it 'secure enough'.