I bought a 335d Touring for our first one, and found it adequate. Just. With ~460L. You could easily fill it on a day out with all the crap she wanted to bring with. Note that the saloon has the same boot capacity as the estate in the e91, but with all the added hassle of a tiny opening to put stuff in, and unless you luck out finding one where the original owner specced otherwise, you will likely not be able to fold the rear seats down.
When the second was born, I swapped it for a 530d Touring. With 560L it was MUCH better. We went camping with it once, albeit for only a couple days, and we did manage to get everything in there. Just. Same with a 10 day trip daan saaf to London town. Obviously swapping the tenting stuff for extra clothes, but we did manage to squeeze everything in there.
Now have a Seat Alhambra (same as Ford Galaxy / VW Sharan), and it is easily the best family motor we have had. Ample room, spare seats when we need them, but the real bonus is with the width. The middle row is 3 full size seats, which means, even flanked by the kids high-backed boosters, fat knots like me can still sit in between them (climbing over them to get there is a different matter mind).
Of course, people hate them. And I kind of get that. But on the flip side, it is the most useful motor I have ever had, having once just thrown a double sofa-bed in the back (with the seats out of course), or a big sheet of MDF from B&Q, or even just throwing the pram in, fully assembled, because it was raining. And all at an average of just over 40 mpg (post remap, and while that might not sound overly impressive, remember it has the aerodynamics of a block of flats, and ~165 BHP).
Another plus is when you go shopping, if it's raining, when you open the boot, it basically covers you from getting wet when stacking all the rusks and kids magazines into the back of the motor.
Plus the wife likes the taller ride height. The kids / old folks are easier to get in and out as a result too.
Personally, when it comes time to move this one on, I'll be looking for a newer model. Not something different.
If you want more of a "car" than a "van", then the Merc E-Class has the biggest boot though. By a mile. It's around 100L more than the 5 series. Other than that, the Superb would be a good shout too.