Currently 'Creampie' is translated into 'Ejaculeren in kut of lul'.
This literary translates into 'Ejaculate in pussy or cock' which is obviously incorrect as far as I know. I've never seen someone ejaculate INTO a dick.

A better translation would be: 'Ejaculeren in kut of kont' which means 'Ejaculate in cunt or ass'. Alternatively you could just use the word 'creampie' since it even has a dutch wikipedia page. It doesn't really need translation.