I think that each attempt to make students speak in their second language can be a wonderful and fruitful opportunity to improve their communication skills. It should be important however, to reflect on to what places you intend to take your students. The idea of museum is good, as long this sort of activity is appealing and interesting to students. You just need to keep in mind if the topic of the exhibition is not very interesting, students certainly will not listen, ask questions and/or participate in this kind of expedition. You must remember that you want to carry on this activity in the learners’ second language, therefore it is essential to motivate students to communicate, if they will be bored, they will, for sure, switch to their first language. Good Luck!