North Bull Island or Harbour Howth to park

Hi there, I am new in this forum. We are a couple with a dog, we will come from Spain to Dublin and we would like to find some post to park our little camper where we can reach the center of Dublin in bicycle.
I read posts in this forum about Harbour Howth but I would like to know if I have to pay to park there, and if it is a safe place.
I found in google maps a parking in the sea of North Bull Island, do you think this could be a safe place to sleep or leave the camper alone?
And, is it normal to go in bicycle in Dublin? are there cycle ways?
Are there unsafe places in Dublin?
I hope your advice.
Thanks

Hi Ally, thanks for your replay and the information.
Do you know how much it would cost to go by train or metro from Howth to the center of Dublin?

bull island is a totally unsafe place to park camper the only place to park is howth harbour its 300mts.to dart station which goes into central Dublin costs about 3-4 euros each way enjoy your trip if you want more info just post

Another question
Where do you fill your water tanks in Howth?
is there water usually in gas stations. When I traveled I found many places like France where it is so difficult to find gas stations with water taps to fill clean water tanks.
But in Spain is very simple in almost any gas station there is free water. Usually where do you fill water in Howth or Dublin?