Disappointing to read about @PuttingDownRoots Scout group, feeding pork gelatine to vegetarian children rather than just buying in some veggie marshmallows (found in most major supermarkets these days) for them. If I was -for example- a Jewish or Muslim parent, I'd be horrified to hear about this, and wonder why you were so unwilling to make a small adaptation in order to include my children in the group. Similarly, there are people whose vegetarianism/ veganism is based on religious/ethical principles, whose beliefs should be respected.
The OP comes across as spectacularly ignorant and obviously hasn't thought all of this through very deeply. It seems unlikely that they're feeding their own children "all the available" foodstuffs so also quite hypocritical.
Even just focussing on what's readily available/ grows in the UK (so leaving out 'exotic' foods that are popular in other countries, like dogmeat, land snails, rotten fish, horsemeat etc) have your children really eaten all of the following since weaning:
rabbit, pheasant, quail eggs, whelks, chestnuts, black pudding, samphire, cloudberries, asparagus, duck, sheeps milk, jerusalem artichokes, dandelion leaves, redcurrants, laverbread, goats milk yoghurt, tayberries, pak choi, radishes, acorns, oat groats, langoustines?
if not, why not?