How much time to manage an allotment?

Right, this is a slightly complicated scenario, so bear with me!

Over the last three or four years, I have got really into gardening, but I only have a very small garden. My house overlooks a plot of allotments, and I have often thought it would be nice to rent one, and grow things too large for my own garden. But I know all the plots are taken, and I believe (though I haven't looked into it seriously), that there is a long waiting list.

Meanwhile, my Dad has a huge garden - too huge for him to manage. But he lives about 12 miles away, and it's about a 25 minute drive. Certainly too far for me to visit every day. Lately, he's more or less asked me if I would manage the lower half of his garden. I am considering taking it on, but realistically, I could probably only guarantee once a week (possibly more in summer, or if I really wanted to spend more time there).

I've seen this: http://www.rocketgardens.co.uk/showdetails.asp?id=742 which I think is a wonderful idea. Takes some of the work out of growing seedlings, and also answers the question of what to grow and when (which, as a first timer, I wouldn't have a clue!).

I'm wondering if I could take on my Dad's garden, like an allotment, and manage it with a visit once or twice a week...
Do you think this would be do-able?

 

It's doable, but you'd need some shortcuts if you've got limited time, like growing thru holes in carpets to keep the weeds down, weeding is a lot of work in the season.

 

It's as big as I want it to be, @JWK. Dad has a huge garden, and the entire lower half is pretty much in need of looking after. It used to be laid out as a veggie patch, it wouldn't take much work to restore it, just a lot of digging.
The site I linked to usually has offers on. I wouldn't pay full price for the 'Constant Garden' idea, but I may consider if they have another discount (I wish I had thought sooner, there was an offer until mid Feb). I just liked the idea of taking some of the work out of choosing and growing from seed - at least for the first year.
I'm in no hurry though, Dad's garden will always be there, so I can either take some more time to research what to grow, or wait until another discount comes along. The main thing is deciding whether it's feasible to take on a plot of land with one or two visits a week. It's just a bit too far to commit to regular visits, but I'd love to grow my own veggies, and some of the flowers that are too big for my own garden.