I think you really need to go test a GR86 but take your kids with you so you can try out seats etc.
My 4 year old fits no problem in the back with the missus in the passenger seat. I am 6ft3" so no chance of anyone behind me without compromising driving position but if needs must I can fit my 16 year old daughter in too. If you are shorter then 2 kids in the back shouldn't be a problem.
Out of all the cars you listed bar the Evora it is also significantly lighter than the others and you can feel that on the road. It is an incredibly fun car to drive on the limit too. In my opinion that is what makes it fun because the limit is a lot lower than a M2 Comp for example.
When I got my GR86 I was also looking at M2 Comps and I would say out of that list would be my second choice.
It depends what you class as fun though. Out of all of them the GR86 will be closer to your Caterham than any of the others whilst still offering more practicality. I wouldn't call an Audi TT a sports car either. Sure it is capable. but if all you want is something which has a powerful engine and surefootedness just get the RS3 instead.
All very valid points, thanks. I'm 5'9 apparently (was measured the other week and appear to have shrunk) and I doubt we'd ever be 4-up in the car. Can put one kid up front and one in the back so not an issue.
Planning on testing a TT RS and BRZ next week, but I foresee the outcome already.
M2 is common and because the limits are so high, I'd probably end up in a hedge or a police station before much fun is had.
Judging by all the reviews, the GR86 appears to be so approachable and have low limits, which is what will make it fun at low speeds and easy to get the tail out, etc.
TTRS would probably make a great daily, but that's not what I'm looking for here..