Not suicide, but I'm confused. You're going with your wife and baby, but the hikes are only for you? You want to drive to the end of the road in Ha'ena so that you can hike for 4 miles, but "the least amount of time out of hotel the better"?

I suggested the alternate hikes because those are more feasible with a wife and baby. Also because the drive from Poipu to Ha'ena is long and slow (as others have said), plus the need to reserve a permit or shuttle (as escapefromphl said). It's a lot of time spent for a 4-mile hike.

Sleeping Giant is something you could do with your family, and you can get your adventure on the last stretch. Kuilau Ridge is easy and enjoyable by everyone. The time saved can be used for getting a nice meal in Kapa'a or Lihue. You can go back to Kalalau when your child is bit older and can hike with you. And then, instead of turning around at Hanakapiai Beach, continue upstream to the falls. Or to fully experience Kalalau, get a camping permit and do the whole trail.

In Koke'e, avoid the trails when they're muddy, whichever one you decide on. Awa'awapuhi has great views at the end, and the trail could be done by your whole family; if you want some extra adventure, you can proceed past beyond the railing while your wife and baby stay back. The Canyon Trail that I mentioned earlier is a bit shorter and has nice views of Waimea Canyon instead of Na Pali.

Anyway, whatever you decide, enjoy your trip, and give us a report when you return if you don't mind.