В выходные дни мы бываем в деревне. -- "бываем" (глагол несовершенного вида) means you regularly, every weekend or so, visit the village.
В выходные дни мы пойдем в деревню -- "пойдем" (глагод совершенного вида) means you are going to visit the village this weekend. You are talking about one visit, not regular.
На выходных мы ходим в деревню -- "ходим" (глагол несовершенного вида) means pretty much the same with "бываем", but here you underlines that you hike/walk to the village, not drive.
Please note that in Russian, grammatical aspects of verbs are very important. If you talk about something that has the beginning or/and the end, you should use совершенный вид (this is close to perfect tense in English). If you talk about the action that is lasting or regular, most likely, you need to use несовершенный вид (somewhat like indefinite or continuous tense in English).
Hope, it was helpful :)