Hi, the hotel you mentioned is miles from where the wedding will be, and as another poster said, traffic will be dreadful to get across town. Also the hotel, while nice, is in the middle of the countryside. Nothing around it.
Dublin hotels while they might be friendly to families with kids in general, do not normally provide many child- friendly amenities apart from the usuals such as a high chair. An exception might be the very expensive hotels 4 and 5 star hotels which provide kids clubs sometimes (but usually during peak season).
I would advise getting an apartment or an aparthotel. One place which fits the bill are the Premier Suites Stephens Hall apartments. Some of these are located right off St Stephens Green on Lower Leeson Street which is in the centre of town. You get self-catering apartments but with many of the facilities of a hotel, and in a fantastic location, close to everything.
Another option which is nice is Bewleys Ballsbridge hotel. This is located in a beautiful period building in Ballsbridge in a fashionable area of town (and close enough to Rathmines). all rooms are E99, even family rooms (where he kids sleep on a bed- sofa). This is a very good deal for Dublin believe me. Breakfast is extra but there is a fine restaurant on site. It is located close to good transport e, cafes, bars etc.
Another option , but in a more businesslike area is the Clarion Hotel in the IFSC area. I include this one because it is one of the few hotel to have a pool, might be nice to have to option to bring your DS for a swim now and again.
All the best,