I was a bit
about the party at the graveside too, but it is hard to judge unless we know all the facts, and the programme didn't tell us what they'd do if there was another funeral going on, or if other mourners asked them to keep it down a bit. The fact that they treat church seriously might suggest that they'd be respectful of another funeral going on, but my suspicion is that they'd be less bothered about the feelings of visitors to other graves. Obviously I have no evidence for that, though.
It clearly is important to Paddy to remember his son (and he did say why the firstborn was so important to him - though I wonder if the same would have applied if his firstborn had been a girl), and it did seem to be important and helpful to his wife too, and I think I'm OK with it, as long as there is respect for other mourners at the cemetary too.