Have your ds and dd ever been given an achievement test? You might be surprised where they score on something like the WJ-III (as in a good surprise, just to be clear!). Each subtest is very short and specific - you can google for a description of each to get a feel for what it is - it's not exactly the same type of test they may be getting when they re given "pretests" at school.
What you are seeing with your ds9 in the classroom (not seeming to want to achieve higher than grade level) might just be boredom and or lack of opportunity to show the level he *can* work at.
Sorry I can't help with specific portfolio suggestions, but if you search here at the forums there have been quite a few threads with suggestions in the past.
Best wishes,
polarbear
