I really don't get what's "gross from a nutritional point of view" about pork casserole, or making pork meatballs, or lamb tagine, or lamb kofta. All of which are really easy to make at home, with high quality and/or organic ingredients easily available from supermarkets.
It's not like you're feeding him Dishwasher tablets and diesel.
Raise your son as veggie, loads of kids are raised veggie nowadays, and it's not an issue. Also don't worry about "running out of ideas" - he's 14 m old.
There are many sources of iron/omega 3 that you can also give him whilst staying veggie - and having variety
a bean chilli - with jacket potato or rice. Make any leftovers into a soup for lunch the next day.
Baked beans on toast - add cheese sometimes. Put cheese spread ont he toast. add cucumber/toamtoes/celery/pepper sticks ont he side
Falafal with couscous and veggies.
Humus with bread to dip
Eggs in any form! soft boiled with dippy soldiers, hard boiled on their own, or egg mayo sarnies, fried eggs, omelette, scrambled, quiche, frittata... ad din all sorts of good bveggies like spinach, peppers etc
Tofu - scrambled tofu, fried tofu, tofu fingers (fake fish fingers)
Dried apricots as snack, or part of a tagine or in flapjacks.
Mix flaxseeds/chia seeds into porridge or yoghurts.
Make your own savoury muffins/flapjacks - can add nutritional yeast to this (good source of B12) - also good for using up odds and ends of vegetables.
Cheese on toast/cheese toasties/quesadilla - if you use white bread it's fortified as well.