I took a few months off from gigging after both my sons, I had two bands going at the time of my firstborn, one at the second (2 bands was definately too much to handle with kids). I can totally understand the feeling of playing lousy gigs with an original band, unless it feels really rewarding in other aspects (recording, making music you really enjoy, great band members etc.), adding on top of that a bad consciousness for staying away from home. I myself would probably go insane if I had taken more than a couple of months off though, but it helped that I usually don't have too many gigs (maybe 8-10 a year), on the average week I just go away a few hours one day for practice. On the gigs were we travel a bit further and maybe stay at a hotel saturday/sunday, my wife usually take the kids to her parents and stay there for the weekend, which she seem to be cool with. If that had not been an option though, she might grew a bit tired of it... I don't know. Everyone has different situations though, you just have to feel it out. Maybe wait to do the decision until a bit of time after the kid comes.
On another note, my dad is a drummer as well, had some bands going before he became a father, He took a long time-off from drumming, I guess for at least 12-15 years, until me and my siblings grew up.. He had some health issues as well, but I kind of always felt that I would not do the same unless I was forced to somehow.