Hi Dianna,
My daughter and I have visited many times with Snow White and Dopey in Epcot by the Germany Pavillion. We have also seen Snow White with all seven dwarfs during
Mickey's not so scary halloween party in 2004 and 2008. There is no guarantee that the crew will be there this year, but they might. As soon as you enter the parks on the eighth, look for any character. By him or her, you will find a castmember dressed in yellow. These folks know everything about where and when to find characters. Ask the cast members if Grumpy will be around during the week during regular park hours or during the halloween party. You can also get similar information at any retail store throughout WDW. Ask the retail clerk, to call the character hotline and rely the information to you.
I will share with you that during my last family trip my daughter had her heart set on seeing Alice from Wonderland. We were told when and where we could find her one particular night. We waited there for 40 minutes and Alice never showed. The next day I explained what happened to a castmember and was told that Alice had a conflict and was not able to make it. The character appearances are always subject to change right up until the last minute.
If you do decide to go to Mickey's Not So Scary Halloween Party, get there early. The times we have seen Snow White and all the Dwarfs, the lines were always very long.
Good luck and have a wonderful trip
Michelle