Family of 5 accomidations

I think you really know the answer to your question. As there are five of you you need to tell the B&B or hotel that there are five of you. Unless, of course, you like the idea of negotiating on the spot regarding the 3rd child, and/or having your reservation not honoured.

Nope not an issue of trying to sneak a kid in as cost is not an issue. It is the fact you cannot find places that take 5 all that easy.

You are correct. It is not easy. You have to request family rooms and state the number. And family rooms can be hard to come. In the Europe the vast majority of rooms are rented PER PERSON and that includes children. Not like the US where you rent the room with little regard for the numbers. IF you want a room for five you MUST ask for a room for five. Tell the hotel/B&B what you needs are and they will tell you if they can fulfill your request.

We are a family of 4 and when we went to Ireland in the summer of 2016, we rented "family rooms" .. in most cases, we could have fit 2 adults and 3 kids as most rooms had 2 doubles and one single or in one case 1 double and 3 singles.

If you are mot sure, I would call the B&B or hotel to enquire. Worse case, I ams are that they can add a cot in the room when needed.

Ha! I have just gone through this myself as we are a family of 4 and travelling to Norway, Scotland and Ireland this summer and wanting to all stay in the same room for expense.

Very difficult to find one room that can accomodate 4 and even harder for 5, I imagine.
In Dingle, we are staying in a family room at the Pax B&B.
In Kinsale, we are staying at Desmond house.
In some cases, you may just have to bite the bullet and get two rooms!
I would email the hotel from their website to ask about 5 in one room. That is a lot and most of the hotels/B&B's in Europe are smaller than the US and would not accomodate that many.
Even as a family of 4, in some places, we had to get two rooms.

Also depends on how long you are staying and what you want to see. If you are there for say two weeks I would consider renting a home for a week. It is cheaper than nightly rentals in most cases, leaves plenty of room for a family, avoids the constant shuffling and provides a comfortable base from which to explore. We even rented one place for a week but only stayed 4 nights do to trip parameters and it was cheaper and nicer than any other option. There are numerous options, we use Shamrock Cottages....easy to search, you can find nice places plenty big enough throughout the island.