Originally, all the chapter titles ended in volitional form (~~しよう), so at first I thought "Let's ~~" would be good enough of a translation to show that pattern, until I reached the last chapter title どんな夢を見よう. The pattern is still the same in Japanese, but in English, the sentence structure breaks entirely because it becomes "What dream shall we see"...
In the end, with the help of my friend Abbi, we decided to show the importance of the pattern through "-ing" and "together" instead, hence why every chapter title ends with it. But to make it work smoothly, we had to paraphrase a bit, especially the chapter title 楽しく遊び回ろう (Hanging out together).
Without a special sentence structure, the titles in English would be:
水族館へ行こう Let's go to the aquarium
お友達も呼ぼう Let's invite friends over
楽しく遊び回ろう Let's have fun in all kinds of places
どんな夢を見よう What dream shall we see
Akira's Comment: "In Enstars, if the heroes are Ryuseitai, then the anti-hero would be Madara-san. (The student council president would also be similar to that, but I personally prefer calling him Dark Hero.)"
Thank you Abbi for JP proof-checking translations for me, and Spoon for being my proofreader!