That sounds tough, specially when you describe your son being hungry and the baby crying. I have three children and complex dietary needs so I get it!! We are gluten and dairy free but not vegi and eat eggs so can't give you my full list!
We don't eat beans or lentils but you can make bean or lentil soups and stews. I used to look up recipes then pare them down so they were simple but still tasty.
Puy lentils, carrots, onion, garlic and some herbs works.
Red lentils with a little garram masala and fried onions.
Roasted chick peas are a great snack and get your foodie husband to work out a simple aquafaba recipe to make omelettes with the chickpea water. There are loads on line but all seem to need extra ingredients so I wouldn't want to be the one trying those out! I am too scarred by years of tears trying out recipes with strange ingredients that result in inedible food to suggest that for you.
I got a tip from Lucy Burney link at the bottom and I always cut up some vegetables for the children to eat while I am preparing meals.
And if anyone is hungry.. there is always a packet of rice noodles, gluten free low salt stock cube or herbamare and as my son used to say.. scraps of meat (tofu, salmon, prawns) and I use the vegetable peeler to put a few slices if carrot and courgette in with the water. Healthy instant noodles.
Keep loads of rice cakes in the house, staves off any hungry person!
Easy meals:
Rice and salmon, with time this can get better with a few carefully chosen herbs and spices.
Roasted vegetables (potatoes, sweet potatoes, courgettes, peppers, carrots)
Jacket potato with vegan cheese, coleslaw / tuna made with egg free mayonnaise
Pasta vegan pesto and courgettes with rocket or spinach.
We eat a lot of rice, I buy it in bulk 5kg. We mix it up by buying rice wraps and sushi wraps but my kids are older so this is something they can get involved in.
I have also found myself making several meals but I really try to limit this as it's just too hard. We eventually found a suitable sausage that fitted everyone's needs for example.. but being wheat free and vegi is quite an ask.
For breakfast, do porridge so they are not so hungry at lunch time.
I have lost count of the times I have written a list of meals we can have and stuck it up on the wall. Even if your husband doesn't have time to help cook, he can help with the brain storming, list writing and help to get things organised.
www.amazon.co.uk/Optimum-Nutrition-Babies-Young-Children/dp/0749926228/ref=sr_1_1?dchild=1&keywords=lucy+burney&tag=mumsnetforu03-21&qid=1594390096&sr=8-1