Absolutely. I'm a serious 5-pointer, and I take missionary work as vitally important to the church. Keep in mind, though, that the mission field doesn't have to be overseas - it could be next door.
Reformed Theology puts the Great Commission in a slightly different context for me. I don't have to go into all the world and preach the Gospel to all men because someone might go to Hell if I don't. I have to do it because I love God and want to obey His commandments.
Yup; you’re right. All this 4-points, 5-points, etc., is so stupid. When I was in Seminary it was cool to do the TULIP discussion to death. (It was the ‘60s, and that’s as “radical” as seminary students got. :) Pathetic, huh?) Even though I’m with the 5 group, the whole thing is not really an issue. Be a missionary. Period. End of story.