Thanks everyone for your replies and ideas - have only just remembered to check this thread!
Our lawn is 160ft by 45 ft - hence my hubby thinking of chemicals rather than hand-weeding. (I would prefer hand-weeding although it's easy for me to say don't use chemicals, dig them out; my back problem prevents me doing more than five mins at a time without getting very stiff and sore and I'm about to give up on my veggie patch for good cos I can't keep on top of the weeds there and don't want chemicals there either.)
So far I've avoided any area with buttercup or daisy - Vedra warned me buttercups were toxic - and haven't tried them on clover yet. I've taken the approach that if in doubt leave it out!
So far the piggies have been fine but come to think of it, hubby used feed and weed about 4/5 years ago when we first moved here. Oh dear.
I like the idea of a piggie patch very much. It would have to be a good size cos I notice they do tend to munch grass down to the ground! When we replace the shed I was thinking of reorientating the shed 90 degrees and creating a piggie path near the shed in the shade - as mentioned on previous posts, we don't have much shade come high Summer. But all this will take time, and diggin up the soil tends to stir up weed germination.
Has anyone else grown a piggie patch, and were you happy with it?
From what hubbie has said, feed and weed has to be applied when the grass is growing strongly. I think on balance we need to be sensible and avoid using it. Perhaps given the large area we will have to compromise and leave half the area untreated..hmm, it's just occured to me that we mustn't use feed and weed near the fruit trees we have planted at the far end of the garden either cos they are on a dwarfing rootstock with roots nearer the surface.