That is up to you. The venue is ~20 minutes from the Dublin airport so car rental is not necessary as you can get by with taxi/ride share. If you prefer to drive, feel free to rent a car.
The closest hotel to the venue is the Castleknock Hotel: https://www.castleknockhotel.com/. Transportation will be provided to and from the Castleknock Hotel. You can also stay in Dublin (20-25 minutes away) however, transportation will not be provided. You can Uber/taxi to and from Dublin easily.
Formal / black tie optional If the weather allows we will be outside for cocktail hour so plan to bring a jacket!