fair play to ye, Fionntáin
I would think that the bodies that promote Irish-medium education would have suggestions for pro-active parents such as you and your wife.
Gaelscoileanna
Comhairle na Gaelscolaíochta (promoting Irish-medium education in Northern Ireland)

Comhluadar is an organisation for families raising children with Irish. They can provide "a free stater pack of Irish language books provided by The National Reading Council." ("pacáiste leabhar Gaeilge ata ar fáil saor in aisce ... le dea-mhéin An Tionscnamh Náisiúnta Léitheoireachta")- I hope that info is still current!

there are some Mudcat threads about Irish-language Christmas songs, Jingle Bells translated is one topic, which may be of interest to you.