If he can't eat milk products, eggs or nuts, it's just a case of finding protein rich foods which he can safely eat, and I understand you not wanting him to be having tonnes of meat due to the potential health affects of excessive amounts of it.
Try these foods instead:-
- oats are a good source of protein, so porridge may be a good choice. Another benefit is that porridge oats are also high in fiber, which will help to keep him feeling fuller for longer
- broccoli is high in protein, so it could be added to a smoothie for a boost not only for the protein content, but also for the benefits of vitamins C and K and fiber.
- different kinds of fish such as tuna - although not an immediate breakfast choice - is rich in protein, so this may help.
- quinoa is also of benefit.
- breads which have been fortified with protein or have protein rich seeds - like pumpkin seeds - toasted can be a good choice
- if you're having difficulty, then you may want to consult a doctor who can refer you to a dietitian for assistance.
Hope this helps.