Can you afford it? I'm one of a very large family (more than 7) and my childhood was not the idyllic happy family sterotype of the Waltons.
Be prepared to not be able to afford to give your children any advantages in life. Wave goodbye to holidays, university education, afterschool clubs, music lessons and sports. You won't be able to afford them. And don't make the mistake of paying for some of your children to attend and not others. This will be noted and the resentment stored. Train your children to expect never to have clothes bought new for them or to expect a room of their own. Be prepared for the fall out from this during adolescence (all those hormones in one room!!)
Be prepared for the fact your children may loathe each other and spend their entire lives fighting, bickering and relentlessly putting each other down. Accept that, with that many children, a spontaneous day out, by the time you've found 7 sets of shoes, coats, hair brushing, arguing with the older ones who don't want to go, dealt with the arguments of who sits where in the car (if you have one large enough) simply won't happen. Should you find an activity suitable for the entire spread of ages, don't think that you will enjoy it. You will spend your whole time chasing the smaller ones, chivvying the older ones and breaking up fights.
Sorry, don't want to be a downer about your plans, but the reality is usually a far cry from the wish. I grew up in a town with a large Catholic population where large families were the norm. I saw the same issues in all the big families. One of my friends had 4 sisters. When adolescence hit, they all synchronised their cycles and, with the family tendency to PMT, their house was a dangerous place to be one week in four. Knives would fly around the kitchen. Sharp ones.
Also be prepared for the large family to have a profound affect on your children. I get on with most of my siblings. There's only one I don't talk to. However, I live half way around the world from most of them and the ones who live in the UK I see once a year, on average. And that's the ones I actually like. All of us are the same. There's one brother who we hear from every 5 - 10 years. Again, not an unusual reaction as many of my friends from larger families act in a similar way.
A good indication of the affect of a large family upbringing is to look at the number of children people have afterwards. Of all of my siblings, only 3 of them have 3 children, the rest of us have one or two. And of those 3, I know that at least one of the children in each family wasn't planned.
Weirdly, I was having this conversation with my neighbour (a mother of 4) last night. Even with 4 she recognised a lot of the antics I was describing.