しかもこんなオマケまで見られるんなら、ほんと、子供の頃にも遊びに来るんだったなって
Furthermore, if i were able to see this kinda of bonus (sunset) , honestly, i (should have?) came here to play when i was a kid.
There is an entry for なう meaning "to do" as a suffix, but how does it convey the meaning that i think it conveys in this sentence?
should have = んだったなって ?