Liked the stay a lot. Very clean and nice apartment. Great view. Note that apartment has 2nd bedroom on 2nd level, which has steep stairs - small kids/old people need to be very careful.
Arantxa is very responsive and welcoming host.
Mutriku is small town, good for kids as beach is shallow. There are nice sea pools, in case of waves, but may be deep for kids. Even some fossils could be found in the cliffs. Very nice location.