exotic, you quoted: "My children are lifelong vegetarians"
and responded:
"Only on a very short life so far.They can and will make up their own minds later; they may follow or they may not."
Well that's a bit on a tangent-ish and nit-picky isn't it! :o C'mon, you know what I mean... that they have been vegetarian since birth. :)
(And they are 14 and 16 and so far how nothing but a strong and morally-based desire to continue being vegetarian, if you're interested!).
On topic, and I know that there are two camps on this, IMHO it is down to the parent in charge on a day to day basis to (within reason) make moral and health related choices for their child, be that not to eat meat, not to eat sweets, to eat meat or whatever. Even giving your child meat is a choice, albeit in England the 'default position', IYSWIM.
At the moment the mum, as (as far as I understand it) the parent with care whilst Dad sees DS for weekends, has made a decision on the behalf of her minor to live a vegan lifestyle. Nothing wrong with that per se, lots of children and adults do and are healthy on it. It's legal, both in general and in her circumstances although it can be argued that the agreement is that Dad feeds son a veggie diet and no more though I SUSPECT (but am not a lawyer) that this would mean that by court order Dad cannot breach this and feed meat but mum is ok under the order to make that non meat diet further so by going for the vegan option.
The issue isn't whether the child might make up his mind to differ when older but that now, as it stands, the mum may well have the law on her side as far as I can see. However, is that a PITA for the OP? Yes! Is that a worry for the OP and her DH?Yes! Is the giving to the child a vegan diet impossible for the OP? No, although it will take some adjusting to.
But is there more to this than the mum's desire to feed her DS a vegan diet on moral or health grounds? I think so. Will it lead to mum playing more control games? I fear so.
It MIGHT be a good thing though. I was a veggie cheese addict and am certainly better off now I don't eat it (vegan cheese is vile!) and now I only eat vegan chocolate. If the OP can establish good healthy vegan eating practices when her DSS is with her (and DAD should be helping too, it's his son!!!!), which DSS can understand are healthy, tasty and morally right he may go home and "teach" mum some of that logic and some of those recipes, telling HER as he does DSM all about it as, as the OP says, he is bright enough to question her about foodstuff.
If, as well, the OP or her DH can cook a vegan meal for the whole family (ok maybe not baby if she prefers not to), it will make cooking after a long day at work easier AND it might make DSS feel not just less "different" but also understanding of how he can eat according to what I and many feel are valid morals in a happy environment, which can only be a good thing.
Disclaimer: Am STILL trying to find nice vegan cheese and expand menu list for me, so know what a fecking PITA it is!