I have a five year old who "plays workshop" and "plays office", all the time! The only other activity I ever see him doing is measuring himself. I also have a eight year old, and he's totally opposite. He's always in the dirt, and playing with toys...It's so weird!

He.... "measures himself"? And you're not concerned with this behavior in one so young?

Yes, actually I am concerned. I always praise the youngest when I make him play with toys and such.
As for the oldest, he now does much of a variety of activities, which is good!

Now that their younger sister was born though, they started acting very bratty... I think they might just be jealous though, but for that I'm making the dad play with them more (although I'm not sure if this will help...

What's wrong with a kid measuring his height? That's a typical thing for kids to do.