17-70mm - definitely for wedding dinner shooting, more versatile.
You will have space constraint when taking in 50mm.
Unless you have a second camera for the 50mm lens.
50mm and 17-70mm - both are ok for street portraits
50mm gives you nice bokeh
while 17-70mm gives you details for your background.
Street portraits will have time for you to change and experience both.
* pls note that 17-70mm can produce nice bokeh too.