De or het festivalcamping?

The correct Dutch article is:

de festivalcamping

Rule Words ending in -ing: almost always de. See the rule

How to use festivalcamping

the festivalcampingde festivalcamping
this festivalcampingdeze festivalcamping
that festivalcampingdie festivalcamping
our festivalcampingonze festivalcamping
your festivalcampingjouw festivalcamping
every festivalcampingelke festivalcamping
which festivalcamping?welke festivalcamping?
a big festivalcamping / the big festivalcampingeen grote festivalcamping, de grote festivalcamping