Hello Stuart,
As a father of four (all grown up) and now a grandfather of eight, I can tell you that there is no finer vehicle for your circumstances. I only wish the Beach had been available when our kids were young. Having said that I could never have afforded one then.
We have a seven seater T6 Beach and I have yet to find anything that it doesn't do well. You can use it as a mini bus, a beach hut, a sports pavillion, a removal van, a mobile office, a secret off grid bolt hole on wheels, a brilliant tow vehicle etc etc........oh and as a camper van it is second to none. The down stairs bed is huge and theirs another upstairs. The storage possibilities are über flexible and there are numerous companies making all sorts of very imaginative camping accessories specifically for the Beach. So you should be able to taylor make your storage to suit your personal needs and here's the best bit, none of it is fixed so this vehicle is incredibly flexible.
Options:
1. If you do decide to get a Beach Camper then I would say that number one on your option list should be the diesel parking heater. It turns the van into a 365 day a year camper and has other major benefits as well. You can defrost the van whilst still having your breakfast just by pressing the heater remote from the comfort of your house. When it comes to doing the school run the van is already toasty warm with no ice to scrape. Trust me you must get this option or your family will will never forgive you.
2. With the three seater bench seat you will need some form of mattress to make it comfortable for sleeping on. There are all sorts of alternatives but it's the "VW Comfort Mattress" option that is IMO, the one to go for as it converts a bumpy undulating bench seat into a perfectly flat bed. It's underside is contoured to mirror the bumps in the folded bench seat. You may find it rather hard though so don't be too misled by the term "Comfort". Think of the Comfort mattress as the starting point in constructing a comfortable bed. It isn't that comfortable but is IMO, essential as a base platform.
Useful game changing accessories:
1. Brandrup Isotop roof liner: Makes the roof warmer, darker, almost draught free and keeps the damp out.
2. Pull out boot tray: this is also a game changer. Without one the thing you want will always be buried in the depths of the boot and will almost always nessesitate you having to kneel on wet grass to tunnel in under the Multiflex board to find it. With a pull out tray you can instantly access anything in the boot.
3. Water proof seat covers: With kids and dogs they are an absolute must.
4. Compressor fridge/freezer: These things are expensive but essential when camping.
Good luck and welcome to the forum.