Hi there, what part of North Dublin are you from? There is loads of threads in here about north Dublin in general. You need to make 3 posts before you can see them. To answer your question, yes you can fish in Greystones Harbour. I prefer the beach though as your more likely to catch fish
. For kids it’s not the friendliest of walks to get to the best spots so 2 things I recommend if the pier doesn’t work out. Hire a boat from Dalkey (weather permitting and make sure it’s a really calm day) - pretty much guaranteed to catch something!!
If it’s windy then try the beach for flats and spinning for bass. I live in north Dublin and if I’m looking for a good session tend to head south of Killiney as the beaches are Generally deeper than Dollymount to Dundalk!