AuburnLavender, that sounds like a pretty good variety for a start. I've worked with some two year olds who would only eat 2 or 3 things ever. Some ideas:
Will he eat any sort of spread on the wraps? Hummus, nut butter, yeast spread, etc.?
Does he like dipping things? You might try some sauce/hummus/cheese (even ketchup?) etc that he likes and let him try dipping in vegetables or bread. One of my nanny girls was very finicky about veg, but she would eat all sorts of stuff if I served it with hummus.
Does he eat tomato sauce on the pasta? You can puree veg or proteins and hide it in the sauce. Carrots/sweet potatoes and red lentils all work well, because of the color.
Would he eat samosas maybe? Potatoes, peas, cooked carrots, cauliflower.
Maybe a mild curry?
There are loads and loads of good mock meats that you can get at large supermarkets or Holland & Barrett; he might like some of those while he's getting used to a different way of eating. I wouldn't base a diet on them necessarily, but once in awhile is fine. Also, they vary in quality...some are very chemical/processed, while others are minimally so. Redwoods (in Holland and Barrett or a hfs) makes some fishless fingers, but I don't know what they're like as I was never a fan of fish. They also make some nice cheeses, again maybe something to use in moderation. If he likes a cheesy flavor, Engevita powder is good for adding that..use in sauces, etc. Our munchkin (I am Indian Summer's other half) really likes these Tofu dogs that we get from Waitrose. The brand is Taifun, and they sell them other places too. They don't have any preservatives or scary stuff in them, so I'm happy for her to have them occasionally (they are a bit pricy though). If you look on the product thread in the UK forum here, you might be able to get some ideas about what sort of specialty vegan fare that people think tastes nice, and what stores they get it from...not sure what shops are available to you.
Regarding vitamin supplements, we give the bean a Vitamin D spray each day. This is recommended by the NHS, etc. for all children who aren't formula fed though, regardless of diet, primarily because of the lack of sun exposure most kids get here in bleary England. Our little one is still nursing quite a bit, but over this next year as that changes, we're going to give her a B12 spray or drops as well. We eat a vegan diet, so she gets very little B12 in her food other than breastmilk. If your guys are still eating dairy and eggs, they will probably be okay, but you can give them a supplement if you're worried. B12 is a water soluble vitamin, so they just wee away what they don't need, you don't have to worry about it building up in the body or anything. Some dietitians would suggest that vegetarians/vegans need to be extra careful about iron and calcium in their diets, but I find that it really is no harder than if your kid is an omnivore. One of the things to keep in mind is that it's okay to look at children's diets over a long timeframe, say a week, as opposed to every day. If your two year old has one day where all they eat is blueberries and tofu, that's okay as long as they get something different over the course of a few days' time.
There is a good page on animal-based ingredients here:
http://www.food-info.net/uk/qa/qa-fi45.htm, with a list of e-numbers etc. Fortunately, most processed foods in the UK which are suitable for vegetarians are labeled as such.
I'm not sure what to say about eating at their dad's place, but I think there are some others here who are in the same boat, who have an ex who's not vegetarian. With an 8 year old, I'd tend to say that she probably needs to make that choice herself, but I don't really think there's a right or wrong here. Is their dad pretty easily to get along with generally..I mean, if it's going to be a huge argument then that's something to take into consideration too.
Whew...sorry to be so long winded. Our munchkin is a terrible sleeper and having this uninterrupted time to post something finds me typing out all of my thoughts! Welcome to VV!
There's no such thing as a stupid question so feel free to ask away. Here's a few links that might help, along with a blog by a good friend of mine who's raising two vegan boys. 
