Congratulations on your forthcoming little one. They are a marvelous learning experience!
My suggestion would be for 2 bags...one for the baby necessaries, which, in my experience, is always full, and the other, perhaps matching, for camera gear. Or different, to tell them apart, avoiding the
unthinkable
The "Slinger" style of bag comes to mind. I can't remember who sells it now, but Spiratone used to, in the Stone Ages.
In the case of outings with the wife and offspring, the watchword is "light" and plan ahead...one lens on your camera may be all you need, (Get to know it, and what it can do for you...it'll be
much more than you think.) at most, one other lens, and minimal accessories, such as flash, filters, spare batteries, memory, and cleaning gear will make the day much better. (Little chubby sticky fingers do find lenses almost automatically, you know.) Enjoy that...they grow up so fast!
Just looked at your equipment list. I don't really see the need for another bag. The D 90 and 18-105 are as good a "walking around" combo as there is! 27-~155 mm equivalent on your DX body..."hog heaven", I calls it!
Of course, if you need to carry extra stuff, like your flash, a filter or three, extra memory card, cleaning equipment, which can all be compact and light, Cargo pocket jeans work fine, or a belt pack of some sort or, a surplus field jacket, or bush jacket with the extra pockets.
Orrrrr...a photo vest! They look cool, and carry lots. (but,you don't have to)

Back to the original premise...disinformation...didy bags, no logos yelling "STEAL ME!" go light...And, at the end of a long day, your back will thank you! Enjoy!