I think there are some ways how to expression about that your situation. Please refer to the following and choose which is the best to tell someone in your situation with your feelings then. 昨日の夜 (or 昨晩 as formal expression of respect than 昨日の夜) 、 私たちは日本で何がしたいかを話し合いました。 The sentence has nuance is a bit close to "had a discuss" with someone. Like "put our heads together" for making the plans what will you them to do in Japan, detaily. 昨日の夜 (or 昨晩) 、日本で何がしたいかを語り合いました。 The phrase has feelings like "You talked about dream" without care the time for chatting. For example, "I wish I can see HOTARU them." "Oh, that's sound lovely! And it's also nice if we will able to top mountain climb and have experience ZEN, too." "Cool. If we had the chance to go, let's try to do it, too."... Even it's a difficult thing to do them in reality. There are still other else how to tell. However, I think these phrases are typical expressions. ^-^

昨夜、私達は日本にいるとしたいことを話した。I think. "Yuube, watashitachi wa, Nihon ni iru to shitai koto wo hanshita." in romajii. Maybe a native speaker can confirm for me but that is how I would word it. I would use yuube too for "last night" cos "kinou no ban" is more like "yesterday evening" in my mind. Same difference though.

You sure the time when you talks about It is good. you can exchange the word want to do as like Plan or itinery　It is more simple to make a sentence or this is one chat between accompany in japanese drop off both understanding thing translation is other teacher's advise is good my one suggestion is " 昨夜は日本での事をはなした”　this is most simple one