Where to hide those gifts... I've got some ideas, but I'm hoping to find more.
One great place I've found is the large boxes that were originally holding the Christmas ornaments. They get put back on the garage shelving with lots of things stuffed in. My kids would never consider it. Also, with all the various boxes in the garage, it's easy to slide a large flat one in--looks as if it has always been there. (Tip: Don't clean the garage in the fall; very useful for Christmas.) And all the bags that sit on the gardening shelving unit have a few more joining them for a little while.
My parents used to put the gifts inside the area under their waterbed... I don't know how they did this, but it was a large space inside the base, and difficult to get access to. And handy, since they would wrap the presents in the bedroom.
I have had neighbors house some things that needed assembly and were large (foosball table).
If you have any other creative ideas, or techniques for keeping a gift a surprise, I'd be glad to know!
bebu