Hi there! The correct answer is "nous y allons samedi".
The word "y" replaces the words "au parc", because the word "y" always stands for a location. The place of the word "y" in the sentence is in front of the direct verb.
These two things add up to the following conclusion: the correct sentence is "nous y allons samedi."
Nous y allons samedi. Y replaces = a location (le parc) or a thing as with "en" introduced by a partitive article Nous avons pensé à la maison nous y avons pensé BUT nous avons pensé à Pierre nous avons pensé à lui (it doesn't work with persons, only things.... With persons you have to use "à" + indirect object pronoun = me, te, lui, nous, vous, eux nous parlons avec mes parents = nous leur parlons ............
