September will be warmer and more summer-like, with summer vegetation and maybe even a possible option for swimming a bit.
The tourist season tends to be short in Sweden, mainly mid-June until late August.Edited: 18 December 2017, 22:11
Hi thank you for the info. Looks like we may need to go in April. Is there much activity in April are outdoor cafes open etc please?
April is known for its very unpredictable weather we even call unpredictable weather "april-weather". We swedes do crawe the sun so if its sunny and nice weather there will probably be some uteserveringar-cafés open for some lapping in of the sun and they will probably supply you with a blanket so you dont get too cold. but the big outdoor eating and drinking boom usualy starts in May although the citys ordinances say they can open from the first of april. You will probably find the weather quite cold compared to Australia(just warning you). I am not that well versed in the al fresco dining scene in Gothenburg but this site might help (it at least has the most obvious ones in it). http://www.goteborg.com/en/outdoor-bars/
You will hopefully enjoy Gothenburg both in April and September. Kungshamn is a really small town and some things might not have opened in April or have already closed at the end of September. Some restaurants are only open during weekends outside of the tourist season.
Thank you kindly for the info. Looks like we might go the last two week of sept
Thanks for the reply really good to know