Well, the first cruise we booked a cat 11 midship & were upgraded by
DCL to the category 8. That was a complete surprise and we did enjoy it but we would rather be on the ship in a 10 than at home.

We did see the space difference between the 10 & 11 though & will book a 10 or up for that reason since the two kids will only get bigger.
It is just two flights up the deck 9 and then the legnth of the ship to the drink station. You should probably be able to make it there in a few minutes. We do go down the hall to the midship stairs though in order to avoid the smoking section at the adult pool & outside the Cove Cafe.
As far as the porthole vs. a veranda, we honestly wouldn't use a veranda and the porthole is so big that the kids could both sit in it & look out. On our first cruise they both played with their hot wheels by letting them race down from one side & roll back & forth. LOL! That kept them entertained whenever we were getting ready to go out. We didn't spend much time in our cabin either time.
We have requested staterooms when we have booked in the beginning. I think that they give you a gty room if they have sold out of that category. This allows them to upgrade & shift people around without reassigning them a room. You will find out your room number when you receive your docs.
I also wanted to add that these room at deck 7 forward are fairly quiet in regard to hall traffic unless you have very loud neighbors. The doors at the end of the hall go to the bridge so it is not a thru way for passengers. We didn't hear much noise at all during the week.