I have the Poppy hippie and the groovy. I would recommend the groovy because it has the extra pocket which is very handy. The Kristin hippie has the extra pocket too but it doesn't zip like the groovy, and you have to open the whole purse to access the pocket. I have the larger Kristin and the short strap is very comfortable, but the longer strap is thin and stiff and not as comfortable. They have changed the groovy. The old ones had a cloth longer strap, which didn't look as nice, but was very comfortable. I don't know how comfortable the new straps are, but they look more comfortable than the Kristin's. The new groovy doesn't come in regular leather though. The older ones did. So for looks, you would probably like the Kristin better, but for security and comfort, the groovy is better.
For leather, the Madison swingpacks look very pretty. There is a Poppy leather swingpack that zips closed and has an additional zip pocket. But both the Madison and Poppy swingpacks are smaller than the others and don't have a short strap option.
I know that people always want a swingpack for traveling, but in my experience, when I travel, I always carry more than I do regularly, so most swingpacks are very small. I like to be able to fit a water bottle inside. And with two small children, you will have to carry wipes and maybe other things for the kids.