try Chicken apple sausages. I either heat them in the toaster oven or the Micro as they come precooked. The little bits of apple inside make them appealing to my 2 toddlers. I peel the casing off and cut them into really small bits to make it easier to digest and less likely a choking hazard.
I agree w/ the other Poster about dipping...we call all dips "dippies." My kids are really into anything they can dredge their food through.
We too do eggs in many fashions. Yogurt is a strong staple here but be cautious with the sugar content. I buy plain organic yogurt and add a little agave syrup or maple syrup or honey so that I can control the amount of sugar a little better...or dilute a preflavored yogurt with a bit of the plain. We eat cheese too, but too much cheese and yogurt causes constipation with my two so I am always careful to balance hydration, fiber, and exercise to prevent an issue.
I put sunflower seed butter on toast instead of PButter sometimes since our Pediatritian advises to wait until my son is 3 to do p.b. It doesn't offer as much protein as PB, but it does add some.
We too do soups with beans and/or meat diced small. We have recently added hummus as a "dippy" with broken up pieces of pita or crackers.
I personally try to avoid Soy products while my children are so young and developing. My youngest is allergic to it which openned my eyes to the negs. I allow my daughter who is not allergic- things w/ insignificant ammounts but still think it probably benefits her to avoid it right now too. There is controversy still on the effects of the hormone interuption on small children since soy is a phyto (plant) estrogen. Soy, while sought after for being the only plant based complete protein, has been turning up as having so many suspected problems- hindering calcium absorbsion also...not good for a little ones developing bones. Soy has also climbed onto the list as being in the top 8 food allergies. There seems to be a coorelation to an increase in sensitivity and the routine use of the genetically modified varieties. I used to hold it in such high esteem and eat it as much as possible until I learned more about it. Now I am leary and my whole family uses it in moderation at best.
My husband makes little turkey meatballs with pasta sauce...battered cod, hamburger, and rotisserie chicken for them.
I feed my daughter, 1/2 of a Thomas's hearty grain bagel...with cream cheese or toasted with a little bit of butter, as 1/2 the bagel has 5g protein.
I use beef or chicken broth cut into the water required for things like mashed potatoes or whole grain rice. Perhaps doing this may get your son a little more amenable to the taste of meat in a gentle fashion?
I feel like I spend a lot of time and energy each day thinking about what to serve next to keep the food groups balanced! ...but those are mostly our protein sources.