I'm like you, planning like crazy and fitting our ADRs in so they make the most sense with we will be that day.
Since it is your first day and with young children, I am assuming you will be in MK for the daytime hours and this would be dinner? If that is the case I would reccomend:
1. Kona - because of the easy access from MK and the great food.
2. Whispering Canyon - a little harder to get to from MK (you need to take a boat), but still doable (is that a word? LOL), and I would rank it 2nd in food quality as well. However, if you have lively, outgoing kiddies, they may enjoy the antics more at WCC. Kona is a little more laid-back.
3. Hollywood and Vine - unless DHS is going to be your first park you visit on your first day, I wouldn't suggest it. I have never eaten here, but from what I gather, it is not that highly rated food wise. And remember, H&V only has the Playhouse Disney characters for breakfast and lunch, so if you want to see them for dinner, you won't. You may be better off booking this for a breakfast on an am when you are planning to visit DHS to see the characters?
Now, this is all assuming you will be at MK on your first day.
Just my suggestions, I hope you are happy with whatever you decide. It's so much fun planning, isn't it?!