I've visited the Porsche Werk Leipzig myself last summer, with my girlfriend. We are not (yet) Porsche owners.
We booked a night in The Westin Leipzig, which was just fabulous. Very kind people and very good service. They mistakenly gave away our normal room, so we got a big suite instead (for the price of the room we've booked). So their mistake was quickly forgiven and forgotten
They have a good pool and nice restaurants. On top of the hotel is a restaurant awarded with a Michelin star. The bar of that restaurant is a must since it gives a spectaculair view over the city of Leipzig.
The city of Leipzig is a nice city, and we had some incredible weather that weekend. It's nice to walk around and do some sightseeing. We stumbled upon a fantastic choir in one of the curches there. And we've found a good restaurant that night to.. In conclusion: the city is enjoyable, but not worth a city trip as such. IMHO you can not compare it to London or Paris.
The Porsche Leipzig Centre was an amazing experience. We've booked the Co-Pilot program, which includes a factory tour, a tour in their museum, and 3 very hot laps in a 911 on their circuit.
First of all, people there are passionate about cars, and it shows, they are incredibly friendly (even if they have to work on Sunday). Due to lack of time, my girlfriend and I went during the weekend. We have visited the factory on a Sunday, and therefor there was no activity (we knew that). It was nice to see how clean the plant is, but that's just about it. The chassis comes in painted, together with some big chunks already in place, from an other factory that also produces the chassis for the Touareg. The only thing that happens there is putting some more stuff in and attaching it with some screws. I'm more interested in the bigger work, like painting etc... So for me, not seeing that would not be a terrible loss.
The museum tour was very nice, and they have some milestone cars in their, definetely worthwile.
Like I said, I did the Co-Pilot program in a 911. I have no experience with the Cayenne program. But after my experience with Leipzig, I'm confident that it will be good
My suggestion: altough I'm not a Porsche owner, I had the rare occasion to drive a 911 myself, and I've been in the passenger seat many times. The drivers that were driving are good. Once I did a tour with a 997 whilst the salesman was driving. He drove it to the limit, with a little sideways action. But I had never been on a track. So if you have never been on a track with a sports car, whilst a professional driver is driving, consider to do that whilst your there. (i.e. the Porsche Co-pilot program)
If you have questions, don't hesitate!
Enjoy your trip
PS: when it comes to your little child, contact Porsche Leipzig. For instance, during my 3 hot laps, there was only one passenger at a time. If this is the same with the Cayenne, you can go first whilst your wife waits with your son and vice versa
but I am very pleased with the forum to help me finding out as well as Porsche in the Middle East to be very clear what is possible and what is not 
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