In short, yes. Our 6 & 8 year olds love it:Very interested in these tread.....but have a SL question.....can you fit children in the back, or do you need to cut their legs off (it looks rather tight) ?
(Note, there's also a Border Collie in the front ).
But not all R129s have rear seats - they were an option on some models.
Both front seats need to be moved forwards a bit, not a problem on the passenger side but a tall driver may be a bit cramped. I'm 6' 1" and normally have the driver's seat as far back as it will go, but being an auto it's not that big a deal having to drive with it further forward on an occasional basis.
They are specifically designated as 'child seats' but do not meet the latest EU standard so technically you should use booster seats (which would actually be daft). The roll bar is meant to be raised (switch on the dash) when the rear seats are occupied.
My mum has also been in the back!