If I understand you right, you are going from DB2 10.1 Express-C edition to DB2 10.1 Work Group Server Edition or Enterprise Edition.
If that is case then you shouldn't have any issues. The binaries for DB2 are basically the same across editions. It is just a matter of a license file that enables or disables certain features and enables/disables use of more/less CPU and memory. (The only exception to this I have seen is the DB2 Spatial Extender-for GIS type storage-which normally would be in Express-C, but somehow isn't. So that one you have to download (for free) from IBM's site. But if you did a regular Enterprise Edition install, it is installed.)
Anyway, if you are "migrating" the entire instance, I take that to mean you just need to apply the Work Group Server edition license file or the Enterprise Edition license file to the database instance and Express-C will automatically turn into one of the other editions. If you are talking about moving data from an Express-C environment to another environment, there should be even less issues (pending the database version is the same). If that is the case you could do a backup from one and a restore to the other.