If you're going to give a dog fruit and sugary veg such as carrots, invest in some Logic toothpaste. I've found it cheapest from vet uk online. Don't worry, all dogs I've met love the taste of the toothpaste.
Yes, fruit seeds, grapes, raisins, dried fruits and onions are toxic and shouldnt be given to dogs.
I often mix some apple into the dogs vegetables, which I pop into the liquidiser as it all needs to be finely grated/chopped to aid digestion. My lot love carrots, cabbage, sweet potato, beans and spinach.
Both my 2 love fruit and veg. Infact one of them likes to go round the garden to pick his own strawberries, blueberries, cabbage leaves,runner beans and even pulls spring onions, the latter was a bit of a give away as his breath made my eyes water. Needless to say I have tried my best to stop the helping yourself business. But I give them choped carrots and stalks of cabbage, broccoli etc. And they get a piece of apple or a couple of mandarin segments most days.
My lab loves fruit and veg and I haven't yet found anything like that that she won't eat,even kiwi! I don't give her anything that Jules has listed either. She drools at the sound of an apple being munched. (Also apparently the pips are bad for them but I think in quite large amounts....I take them out just to be safe) Full of vitamins and a great way to vary the diet without making them fat!
My mastiff will drool for fruit much more than he would for meat. He eats any fruit but lemons (and only ever a few grapes) He also loves brocolli and cauli. He helps himself to plums, gooseberries, raspberries and blackcurrants. Never have a poo problem though.