In Need of Advice! My doggie is not a fan if toddlers!

[Moni Badal]

My dog is a papillon pomeranian mix, he is about 5 years old and the sweetest thing you can imagine, unless you are a little kid!! Riley was a rescue and was in and out of a few homes before settling in ours. He seems like the most friendly doggie in the world, but with some other dogs or kids he lashes out. He has never bitten anyone, but definitely shows signs of aggression! Here are some of the common triggers:

1. Other dogs that approach too quickly or get too "in his face", or when too many dogs approach him at a time.
2. When small children, about 2-6 years old, approach him and want to pet him right away or run right up to him.

To most at first eh just seems very docile and shy, his ears drop down, crouches a little, lowers his tail and gets the "whale eye". If this does not deter whoever is making him so nervous to leave (which usually it doesn't, unfortunately nervous dogs also appear to be very cute and safe sometimes) he lashes out, this is when the ears go back, the lips curl and the barking and growling happens. At first I thought it was a matter of him being approached, but once my nephew came over to my apartment and was actually keeping his distance from Riley. When my nephew walked into my bedroom Riley stalked him in there and got very aggressive. I'm not sure if he would have really ATTACKED or not because I separated him and put him in the bathroom as soon as the first growl and bark occurred.

I would love to feel confident bringing Riley to family functions, but it is just too stressful with my nephew also there, and of course his safety is a priority for me, plus I don't want to traumatize him to dislike dogs! Is there anything I can do?