I do not think you will like what I am going to say but I think it is
important. I cannot believe that a foster care agency would house two
children who have difficulties eating with a family that has food
restrictions. Those children need *every* opportunity to improve their
health, and lifestyle choices -- religious or not -- have no business
getting in the way of a child's health. My partner and I and one of
our children are all vegetarian but our other child is not and if I
needed to stand on my head and suck raw beef through a straw while
humming Danny Boy to help him I would. I don't know what advice to
give you because if those children are getting the love and attention
from you and your partner that they need, then moving them would be
awful, but if they're not getting the healthcare that they need then
it's not the right solution either.

As for speaking out about being vegan (you talk about both
vegan/vegetarian in your post so I'm not sure which you are), there is
a middle ground between loudly proclaiming your eating habits to
everyone within earshot and eating proferred meat so as not to offend:
simply say "no thank you." You and your partner have different views
on this, which is separate from your foster children's issues but
should be addressed so you can help them together.

I wish you well. You have taken on a huge task and the children are
fortunate to have such generous people in their lives.

lm (are twizzlers vegan?)