What's so great about children?

Gerald of The Cafeteria is Closed asked the question "What's so great about children?" There are lots of comments (64 at last count) but I thought the question deserved an answer here.
I have always looked at these type of "Meaning of Life" questions in the same way I solve business issues at my clients. Take a step back, strip out the answers such as "But we have always done it that way!" and do a Chesterton type examination.
By the way, you can't really plan children. You can certainly say "No", but you can't guarantee children will arrive by saying "Yes".
Anyway the benefits of children depend greatly on the manner in which you accept them. If you treat them as a burden or expense and focus on the ways they cramp your lifestyle, take away your freedom and give very little return for all the trouble you have taken - then they aren't great at all. This is basically the so-called Devil's Advocate position Gerald posited in his post. But it's all rubbish.
Let's use the same arguments with a new car.

Why bother with a new car? It just costs money, fuel is so expensive and smelly, it gets dirty and you have to clean it, the expense is constant even if you don't use it with taxes and fees, there's no more together time as you are driving everywhere, you lose fitness rather than walking, you have to park it somewhere. And once it gets too old you have to sell it or trade it in on a new one and lose more money. Gosh, why would you get a car anyway?

So, ignoring the silly short sighted criticisms of children, the primary thing children actually do is create parents.
Parents are forced to grow up and take responsibility for their actions. They cannot continue to act like teenagers with lots of money. A Dad and Mum now need to consider someone else. Someone who amazingly looks like them and shares many of their own characteristics - both good and bad.
And do you know the really surprising thing? The more the parents embrace their new roles, the greater the grace of marriage acts on them. They grow closer together despite the reduction in "Me" time. It's the "Us" time that is actually more important.
The children react to the unselfish love and respond in kind. Even children that go to school and are bombarded with "Me! Me! Me!" messages all day can still survive with their family love intact as love is quieter in volume but much more invasive internally. Love sticks.
Children are able to multiple love. Each additional child does not mean the same love must now be divided again. Somehow each child increases the total love more than in a straight mathematical line. If the love between Dad and Mum is 2, a baby makes it 3+x and another is 4+x+y and each one adding more again. This is all contingent on accepting and treating each and every child as a gift (which each child is).
We have found the other great feature of children is they are fun (see the 11th reason) The photo with this post is of Clare and Rose playing with Martin. We have been told that younger children in large families tend to be missed out and suffer isolation. Bah! Younger children get spoiled if anything with too much attention from all the rest. While Ariel only had Lana and I, Martin has 8 other people to give him some attention on lots of different levels.
So, what's so great about children? They made us grow up. In growing up we have enjoyed life far more and participated in so many activities we would never have experienced.