Here's my attempt at the first one - corrections gratefully received, as usual.

Is féidir é go bhfuiltear díolghadhach le gach uile dhuine tar éis dinnéir ar fheabhas, do a dhaoine muinteartha féin fiú.

For the second, I've come up with this -

Bím ag ól deoch ach ar dhá ocáid amháin - nuair a bhfuil tort orm is nuair a níl tort orm.

'É' is superfluous if there's a following clause. Never saw 'díolghadhach' before (I've read very little Irish), but FGB says it's 'literary'. Assuming you can use both prepositions 'do' and 'le' with it, better to be consistent and use the same one. 'Ar fheabhas' isn't an adjective, so would need the verb - 'dinnéir a bhí ar fheabhas'. "One's" is generally "do"(yours) in Irish, but since you've used the impersonal 'saorbhriathar' ("bhfuiltear"), I don't think you can use the possessive adjective, which is, obviously, personal.
My simpler, more literal version:

Is féidir maithiunas a thabhairt do dhuine ar bith tar éis dinnéir mhaith, fiú do do dhaoine muinteartha féin
(Should it be 'mhuinteartha'?)



You need a negative verb with 'ach', or you could omit 'ach' and have an affirmative verb with 'amháin'. If you use the 'ag + verbal noun' form, 'deoch' will have to be in the genitive. Direct relative after affirmative 'nuair' - 'atá/a bhíonn'. But negative form - 'nuair nach bhfuil/mbíonn' ( without 'a'). 'Tort' >'tart'.

Ní olaím deoch ach ar dhá ocáid - nuair a bhíonn tart orm agus nuair nach mbíonn.

Go raibh maith agat, a chara.