We visited in Winter so this may not happen in Summer but:
Be aware that in our open all hours culture, visitors to Dieppe should be aware that The locals like a long lunch. Lots of places close from 12:00 to 14:30, this includes shops and the tourist information office.
Places also tend to shut shop at 19:00 hours, this includes lots of bars and Cafes' so there is not a lot going on after 7pm. There are some places open but you need to know where they are. The streets were all but deserted in December.
Classic cars can be seen in pictures on some of my other Dieppe Tips.
This is the original (1937 to '55) Fiat Topolino 500, which preceded the better known (1957 to '73) 500, which morphed into the 126 (the last small rear-engined Fiat) in 1973.
The second picture of this tip shows more modern classics. A late 1970s Renault 12 and the 1955-'74 Citroen DS. Arguably the 1990-ish Citroen XM in the background is also a classic.