He's not falling-over-drunk. Just making-a-fool-of-himself-drunk. He tends to come back from the pub in the afternoon, slump on the sofa, and make inane comments to them, when they're trying to watch telly, like "Are those the Wattingers? Eh? Are you a Wattinger? Eh? I said ARE YOU A WATTINGER?"
They are three and five years old at the moment, so just think he's being a bit silly and tend to ignore him. But I can't help wondering at what age they're going to get confused about his behaviour and speech and ask me questions.
I should add in his defence, when sober he is a very nice grand-dad to them.