It depends on how much "luggage" and other junk your passengers insist on taking!

Go to a VW garage and look at one or a SEAT garage and look at an Alhambra which is identical and decide for yourself.

Roof boxes can easily be fitted if thats an option.

We had a Seat Alhambra (same car) and 7 up there was only space for a few small soft bags behind the rear seats. We put a 550 ltr roof box on which gives you the capacity of a large boot. I carried a small alloy step ladder which you need not just to put in and remove luggage but also to fix the box to the rails, almost impossible without. Ours was the 90bhp diesel which 7 up and a full roof box was snail like but fine once up to speed on the motorways.

The existing transit tourneo is based on the current main transit van

the new transit custom tourneo or the commerical (identical) equivelent is called the transit custom kombi (the commerical version comes in a short or long wheel base)

It drives like a car and would swall up 5 adults and 2 kids with plenty of room for luggage.

The other option is the Citroen Dispatch Combi.

Fiat sell the identical Scudo People Transporter

If you want a true MPV, it would have to be a Ssangyong Rexton.

7 seats, nice drive, lots of kit, reliable and can swallow 7 adults plus luggage with ease.

And parts of the Rexton have come from Mercedes (engine and transmission?).

I presume the OP is hiring a car for a holiday. If the Sharan is just too small/marginal (please go and look at one to decide!) then perhaps they ought to consider hiring two smaller cars? Price may be about the same and it may be a more flexible arrangement (more fuel though) - plus you dont have so many adults/children enforced to a confined space for prolonged periods. Consider particularly if not everyone are the best of friends!

Yes you can but luggage space is small so your going to have to put it in the 3rd row and the 2nd row on the floor but 3rd row is a small place to sit in and get luggage so people in the 3rd row are going to have to hold the luggage but the only ones you can go in is the Ford Tourneo,Vauxhall Vivaro,Renault Trafic,Nissan NV200,Nissan Primastar but they are very van-like

I also have this car which is a Indigo TDI Sport

Your helpful comment is, unfortunately, 12 months too late.