Can I charge/maintain 12V batteries in parallel?

I would return the Canadian Tire panels if you can, much better deals can be had from Amazon.ca.

if you keep them I believe you just need an SAE combiner but check polarity. Available on Amazon.

https://www.amazon.ca/NOCO-ISCC2-5-Way-Adapter-Connector/dp/B003L643KS/ref=sr_1_2?ie=UTF8&qid=1490794558&sr=8-2&keywords=sae+splitter

Why don't you set the solar panels up in storage to maintain the batteries?