It's a bit late this year, but here's a list of terms/expressions related to the Easter season which we can bump up each year from now on as the time rolls around:

Carghas
Lent

Rinne mé mo Charghas ar mhilseáin
I gave up sweets for Lent

Máírt na hInide
Shrove Tuesday

Itheann daoine pancóga Máírt na hInide.
People eat pancakes on Shrove Tuesday.

Ceadaoin an Luaithrigh
Ash Wednesday

Seachtain na Cásca
Holy Week

Domhnach na Pailme [in Connemara, Domhnach an Iúir]
Palm Sunday

Céadaoin an Luaithrigh
Ash Wednesday

‘Sé Ceadaoin an Luaithrigh an chéad lá den Carghas.
Ash Wednesday is the first day of Lent.

Déardaoin Mandála [in Connemara, Déardaoin Naofa]
Holy Thursday / Maundy Thursday

Aoine an Chéasta
Good Friday /F riday of the Crucifixion

Satharn Cásca
Holy Saturday / Easter Saturday

Bigil na Cásca
Easter Vigil

Domhnach Cásca
Easter Sunday

Luan Cásca
Easter Monday

Déardaoin Deasgabhála
Ascension Thursday

Domhnach Cincíse
Pentecost / Whitsunday

_________________
I'm not a native (or entirely fluent) speaker, so be sure to wait for confirmations/corrections, especially for tattoos.

Just in terms of pronunciation Carghas is Caraíos in Munster.

_________________
The dialect I use is Cork Irish.
Ar sgáth a chéile a mhairid na daoine, lag agus láidir, uasal is íseal

Similar in Conamara.

That's how I learned it. How is it pronounced elsewhere?