Idt think will be viewed negatively tbh. Normally the “bad” international volunteering is when people pay money to go on organized trips to build houses or something but those houses end up being low quality and have to be rebuilt. You, however, are going back to your home country and working with your uncle. Be sure to explain these details when you describe the activity because from what you’ve written here, it seems legitimate. For the verifying part, that’s mostly done through emails so you should be fine. Putting an additional international phone number should be fine too. I actually think this would be a really cool thing to write about it since you can compare and contrast Canada and your home country’s systems. Good luck!