ScanWedge and DataWedge are the same with different names. I am not sure, but it may be that one is for mobile and the other for CE. Or one name was created by motorola and the other by symbol.
If you want to have full control over when and where scanning in your application is possible, you have to use one of the Motorola SDKs (MDKs).
If the device is running Windows CE you need the platform SDK and an EMDK (http://support.symbol.com/support/searchEntry.do?languages=&rwTarget=%2FrfPlayerWidget.do&searchMode=GuidedSearch&searchString=sdk&productLine=SG_MOBILECOMPUTERS_1_1&product=SG_MC3100_1_2&document=DT_SOFTWARE_1_1&cmd=search&productFamily=&contextType=gs).
EMDK provide the API for the Barcode Scanner and other Motorola related features. There are EMDKs for .Net, C and Java.
The platform SDK provides the CE platform files as built for the MC3100 CE operating system. In contrast to Windows Mobile, Windows CE devices are totally free in OS design and so the OEM should provide a platform SDK to enable developers to do programming against this platform.