Hi,
I read somewhere not long ago that the intestinal flora might be somehow connected with rheumatism. This article (
http://rheumatology.oxfordjournals.org/content/38/11/1039.full) says that as well if I read it correctly, and it also states that vegeterian diet could be beneficial in that regard.
On that account maybe you could try out kefir (home grown), but keep in mind I am just a lay person.
If you will be lacto-vegeterian, I do not think you need substitutes. And if you eat eggs, you are surely without problems. Generally try to eat healthy food(not overly processed) and diverse. Legumes are foods you want to get to know better.
If you think vegan, somebody else will have to fill you in. I read that Kombucha can give you the B12, that is not expensive. But others will know better, I am sure.
Can't help you with your parents, mine are still not used to me being a vegeterian after 4 years. In my country vegeterians are still black sheep. My diet hasn't changed at all, I just leave out the meat. And we make our own bread. Works well for me, but I have been eating 'healthy' before.
Hope this help somewhat,
Mykal