Tip for the X-ray:
My husband was travelling to Neuquen on biz and had some equipment, sensors etc. When he got there the guys at security were really interested in how it all worked etc, so he pulled it out, was showing them all different types of tech the crew had with them, chatted with them for ages, the security guys were laughing having a great time with them, so husband took opportunity to ask them a few questions about the X-ray -- one which he asked is -- is it true that if you put one laptop right on top of the other when it goes through the kray, it can't pick up that there are two in there. Answer, 100% yes -- if you lay a backpack or bag down flat on thebelt with one device over the other, the x-ray will just read it as one machine. Now of course there is a chance that they'll still ask you to open the bag, of course. However on the way back from Canada I had a brand new ipad and laptop in my backpack, and had no intention of paying duties -- so did the trick, hid one under the other, passed it through, no problem. Next trip that my husband went on he "nationalised" our ipad -- ie he put it on his electronics declaration form before leaving the country, so even if they asked him about it on the way back it would look as if it had been purchased here.
My easiest way to get through customs without any stops though really is my child -- a woman travelling alone with a baby, looking haggared, baby hopefully crying and they just don't even bother. One time i put my bags through and had loads and loads of stuff, way over 300 USD coming in, i saw the xray guy raise his hand, he was about to stop me, and then saw the crying baby etc and just waved me through. If you're coming through as a family maybe best to make the woman go through with the kids AND the majority of the suitcases on her own, and the man go through separately a few minutes later. Unlike in the USA where they relly do nothing to make it easier ona woman travelling alone with kids, here they really do extend quite a bit of courtesy (skipping lines at immigrations on your way out for instance).