Let me just throw one thing out there since you are new to this, before you get too hung up on the cabin category/location: Don't worry too much about it! I've seen a lot of people get really into planning and then start thinking that lots of the "nice to have" things are "must have" things. I've been really guilty of this myself! So, I'm just trying to save you some of the mistakes I've felt...
We've been in a few different room categories in a variety of locations. There are advantages to almost every location. Upper decks are closer to the stuff on the pool deck. Lower ones are closer to restaurants/clubs. Forward is closer to some things, aft to others, and mid-ship is a compromise. Our best trip was on the bottommost deck on the Wonder, which many people wouldn't have rated as a very great location - we loved it there! Yes, I've heard that some locations can tend to be noisier at certain times of day (depending on your schedule this might not matter much), and some can make a difference if you are especially prone to seasickness. But, don't feel like there's some "perfect" location you must have.
And, while room categories do have some significant differences, you'll have a great trip regardless of the room category, and we've found that these differences ended up being much less important to us than you might think. You'll hear people say how they "have" to have a verandah or they really wouldn't want to go without concierge, but you can (and many, many families regularly do!) have great cruises without those things. Yes, a Verandah's nice, but again, one of our best vacations was in one of the lower room categories we've ever sailed in (the cheapest oceanview we could get).
So, if you find it's easier or just more in your budget to get a room that's not at level X, don't stress about it- you can have a great trip, regardless!