One thing that we eat a lot that you might try is white beans with salt, garlic, lemon juice and sage served over polenta. My daughter also loves black beans and sweet potatoes served with corn tortillas and a little bit of Daiya cheese (which is dairy, gluten, nut and soy free). I puree a can of white beans into my cream of (insert veggie here) soup. I use essentially this recipe: http://familyfun.go.com/recipes/sneak-it-to-em-broccoli-soup-678382/ adding the beans, some nutritional yeast, and subbing veggie stock and non-dairy milk. I usually use soymilk, but rice milk works too.
Here are a few recipes from my blog that should work for you:
This would be easy to adapt substituting sunflower or pumpkin seed butter for the peanut butter:
If your family prefers softer beans - I'd try to find a variety of lentil dishes that they like. They usually go over well being mildly flavored and mix into foods easily (as patties, salads, mixed with pastas, or pureed for a dip or sandwich spread). You can also use other split peas (red & yellow my favories) or dahls.
Other than that, I find chickpeas to be the most versatile and well-liked of all the beans.
As for getting enough protein - I think it's good to remember that pretty much all foods do have protein. Finding fruits and veggies that are higher and making sure you have them more often might help reassure you (here's a protein chart). Off hand, I think things like sweet potato, okra, broccoli & cauliflower significantly higher in protein than other vegetables. So when you can have those and get 4g of protein as opposed to just 1g from other x veggie, make that your choice. (There are some fruits too, but I don't remember those as well nor do I see them on this list - but that would be worth looking into with having a lot of other restrictions in your diet).