Explaining veganism to my four-year-old and vegan diet supplements

[Morecoffeethanks]

I have a dd who is 4 years old. Until now she has had an omnivore diet- my husband eats meat and I decided it’s easier to make sure she has enough iron etc by allowing meat a couple of times a week.
However she has started asking questions why I eat differently to daddy and her. How do I explain in a child friendly way?
The reason I don’t eat meat is the cruelty to animals aspect.
If she decided that she would like to adopt a vegan diet which supplements are you giving to your children to ensure they have sufficient nutrients? Omegas, iron etc?

Thanks for all the good advice. I think we will stick to the bare facts which is what I have done already, “mummy doesn’t want to eat meat because it’s from animals”. She asks a lot of questions anyway so I’m sure she will draw her own conclusions from those.
She has been refusing meat at home the past few months because she can see I’m not eating it.