I take issue with how you’re using “until they’re able to” here. No age was mentioned, it really sounds like you’re implying that they’re not able to make decisions until they agree with yours.
Also not being vegan is not a decision that is going to harm them long-term. Seems like a perfectly reasonable choice to let them make at any point in their life.
https://youtu.be/2iDrbgfPjPY