brandijocelyn, is your DS 6-years-old? I think with the achievement portion, they want to see something recent (the criteria mention 2 years, but I wonder with our younger kids if they might not even want more recent?) that demonstrates that they are 2-3 years ahead achievement-wise.
Others here might be better experts on portfolios, but the portfolio option seemed tricky to us. DD9 DYS took the EXPLORE and DS6 is scheduled for achievement testing to go along with his WISC scores. I simply don't feel talented enough to put together a "good enough" portfolio.
Don't give up - whether you decide to go with another portfolio or achievement testing, if you look at old threads (or even way back in this one), it isn't uncommon to be asked for "more information" and later be accepted. Best wishes to you and your DS!!!