I don't know anything about these, but unless there is an identifying mint mark on each coin that is different from any other coins of the same denomination for this year, you may have already messed up. With items like these, I believe they need to be sent in for grading unopened from the mint. You simply put the mint shipping box, unopened, in another box and send it off. I may be wrong on this. Will all depend on the mint marks on the coins, or some other way to differentiate these coins from any others.
Also, you would be paying to grade 8 separate coins. You will pay for 8 grading fees and will get back 8 slabs.