Bonjour Gersende,
It's great that you are planning a trip this April! 
There's plenty to do along the southern coast of Ireland! What sort of activities are you interested in? 
I'd suggest you have a look at 
our accommodation page and the 
B&B Ireland website for suggestions of places to stay in the area.
Furthermore, here is 
a sample itinerary to explore Ireland's Ancient East from Rosslare Harbour that might be perfect for you
We also have general 
suggestions for Co. Wexford. In Rosslare itself, I can simply suggest seafood restaurants and Rosslare Strand (the beach). If you want to go all the way to Cork and/or Dublin as you mentioned, here's also 
a sample road itinerary between Cork and Dublin along the coast.
I hope these few suggestions help! Hopefully, other members will have tips in the area. Let us know of your itinerary is coming along.
A bientôt,
Antoine