where would you recommend to go?
Zaborek is a nice place to go and it is off the beaten track, you will also find an English section to the website.
zaborek.com/szkolenia1.php
If they are going to be on the Baltic coast, a must see place is Jurata( The Polish Riviera), they have the most beautiful white sand beaches in PL. Also foreigners enjoy going to a place named Hel for some uncanny reason. Below is a link for a place to stay in Jurata, it is not 5*, but is comfortable, well placed for everything and reasonably priced. The best way to travel to Hel peninsula is by train as the traffic jams can be a nightmare in the summer.
helunia.tp1.pl