I'm afraid I don't know if there are guidelines, but just to give you our experience, I'd say ds has meat perhaps 3 or 4 times a week. He'll have ham, bacon or chicken...that's it really, he doesn't fancy other types of meat. He has tuna, salmon and mackerel about once a week each too.
Meals we have other than that would be things like Vegetable and lentil soup, Veg casseroles, pizza...
I think maybe you could increase the amount of fish meals they have as fish is so good for you. Fish pie, kedgeree and that sort of thing as well as good old fish fingers!
Personally I think meat twice a day most days is a bit much, though I don't have a rational reason for that
I think that chicken, turkey, game and fish is ok to eat more of (not sure of exact quantities though) but red meat (beef, lamb and pork) should be limited to once or twice a week. The argument behind it in the book i read was to do with the saturated fat levels in red meat.
Can't remember where i read it but it stuck with me as i've always eaten a lot of red meat and remember thinking i'd have to cut back a bit for ds, can try and find out which book it was in if you want.