My son is 7 yrs. old and has really creative ideas with his bricks. I see it challenging him and wonder, "How can I help develop his product engineering/design skills?" What kind of tasks can I give him? Ideas and/or advice please.
This is a tricky question and really depends on the individual child. For my children I sometimes provide them with Lego sets that are too complicated for their age and we build it together so that I can teach them as we go. They build until they get stuck, or something isn't working right, and then I help them solve the problem. They are usually very proud of the end result and appreciate the functions of the more complex sets. When a set falls apart I encourage them to try to fix it themselves before asking for help.
I also have them "help" me with fixing things around the house, or on our cars, in hopes that they will pick some of it up just from being part of the process. I try to talk through what I'm doing, and why, so they are involved to some degree.
Here are a couple links to some sites with Lego related ideas with varying degrees of difficultly to help you get started: