I agree, some people can't be Vegetarians because of health issues. But it's healthy for you if you don't have health issues and if you become a Vegan/Vegetarian, eat the right foods, exercise, and stick to it. Don't just decide that "meat is too yummy and you must eat it" or "it's too hard". It's really not when you get the hang of it. I'm a Vegetarian and I do Track&Field, Cross Country running, and sometimes soccer. Not to brag, but on my Cross Country team I one of the top 10 runners, I've come in 3rd, 2nd and 1st place at some track meets, and I do well in many other sports. So it's untrue that Vegans/Vegetarians don't get enough protein.
It's not impossible for vegetarians to be good athletes, but it is much harder in some sports. I absolutely craved meat during off-season weight training, and it would have been hard to substitute for it ... and no, that was not a football training program, that was in my post-football soccer days. In long-duration sports, you get most of your energy from glycogen, which you get from carbohydrates. I didn't eat meat heavily during the season, but I did eat some every day. Carb-loading during the season was the in thing when I was playing, though. I did eat a lot of meat during the off-season, mostly to aid in recovery from weight training. I also found that I really wanted meat after particulary hard matches, though, so I went with following the cravings.
My wife's a vegetarian, so I'm somewhat familiar with the dietary requirements. I would have to say I would have been hard pressed to find a way to play midfield on a vegetarian diet. If you're going to compete at top levels on a vegetarian diet, you'd need a really good understanding of nutrition.
You probably need to pay far more attention to carbs for cross-country that you do to meat, but you'd need to find something to replace the protiens from meat during post-race recovery days and during off-season weight training, as well as finding other sources of iron. I'm not a big fan of supplements, such as the "iron pills" the OP mentioned. Most of the supplements out there are being peddled by people just out to make a buck. There's a lot of advertising behind them, and minimal, if any science. They're not regulated, so anyone can bottle just about anything. You may need nutrients that take a long time to be absorbed, and if you get them from food, it works ... try to add them in a pill form, even eaten with food, and many go right through you. If you're going to use supplements, do your own research into the science behind what you're using. In many cases, they're just a waste of money, and in some cases, they're actually dangerous.