On the bright side atleast your open and honest about all of this.
The main advice people will tell you is to leave them there. Last thing you need is replica firearms getting taken at the border. Going through customs is bad enough when its not smuggling.
Sell what you have, come back to Canada, wait till your 18. When that happens you go and get age verifyed and then by new guns. Its how it works here. And its probably the most common answer your going to be getting.
Any how good luck with it all and I hope something positive comes of all of this.