What you can do here is create a job file by selecting the required tables from Import External Data Wizard. You can edit the job file and replace timestamp with datetime and run the job file. This will solve your problem.
Additinally it is not possible to distinguish a TIMESTAMP and DATETIME when using ODBC, as ODBC has only one data type for both. We map to TIMESTAMP as default (because we need to choose one of them), but user may need to remap.