A picture or two would help greatly, if you can post some.

For function, I prefer not to have a rug the the kitchen. It is a PITA to have to vacuum and wash it vs. just sweeping and washing the floor. That said, we also have hardwood floors throughout our main floor (including kitchen), and they have not held up well at all to all the traffic and heavy use in the kitchen. Our builder insisted that the water-based sealer they used on our floors was as good as the old oil-based sealers, but it definitely isn't. We are vigilant about cleaning up spills/splashes as soon as they happen, but in spite of that the floors have taken a beating in the kitchen. We finally broke down and added a runner (we went with a Ruggable based on recommendations here) about 6 months ago to help protect the floor until we get around to having it refinished. It's okay. It's annoying to have to drag the vacuum out instead of just doing a quick sweep when crumbs accumulate (which is often with lots of cooking + 2 tweens in the house). I don't wash it often because we don't have a spare cover, but it hasn't shrunk (I air dry it). On the plus side, messes have been easy to clean off of it, so spot washing is usually enough to keep it looking clean. There is one corner that sometimes curls up slightly and drives my husband crazy. It doesn't bother me at all. If your floors are pretty bullet proof or you don't cook a lot, I'd do without a runner for function, but if you spend a lot of time in the kitchen and think the floor will need the protection, or if you just like the look of a runner, Ruggable is a decent solution. It's not all that soft underfoot, but it does the job.

Another vote for mixing styles! I struggled with this at first too, and have made mistakes along the way but learned from them. One thing I always make sure to do now is to consider all the different perspectives from which you'll see a rug and make sure the rugs you'll see at the same time don't clash. As Kristina mentions, you can do this by either tying them together with color or pattern and/or by having one be relatively neutral. We have a very colorful antique Persian Heriz in our living room and a geometric rug by the back door that are very close to each other. The geometric rug is a brownish gray and cream, colors that also appear in the Persian rug. Opposite the back door is our kitchen, where we have a Ruggable runner with a Moroccan print in a similar brownish gray and cream, so together they all work even though each has its own unique style/print. To give a visual, here's a picture showing part of the Persian next to the geometric print rug: And one showing pieces of the geometric and the nearby runner:

The reason the sofa has to be on long wall is because it provides more open set up. It is easy to change your cable location. So, up to you but just wanted to make sure you understood the logic. Your son is adorable!!