Update on how this turned out:

Anubis, even though coached intensively in ancient Egyptian, decided he wanted to sit down and work at wrapping the mummy with linen strips. He never did say anything, and just watched everyone go by.  This was not at all what I intended.  My son is 6'3", and with the mask would be almost 7' high at the ear-tips.  I thought that would be intimidating, but he got involved in the linen wrapping and chomping Halloween candy. After the first of the two nights we were open, I was a little exasperated with him, and told him that if he was going to make a mummy, at least he should not tie the strips in knots.  I unwound the mummy and made him do it over! I also cleaned out the candy wrappers which he had conveniently stuffed inside the Anubis mask, since I had sadly neglected to place an ancient Egyptian wastebasket in the scene.

I thought I would have better luck with my daughter as the Mummy.  She was hidden around a corner and was supposed to sneak up behind TOTS as they looked at the blucky in the styrofoam sarcophagus. She kind of sauntered up behind them, but never made a sound.  I think some of the fast movers didn't even notice her and made a beeline for the exit. The scariest thing she did was tilt her head to the side, making it look like her head was a little wobbly.  (You can see these sad excuses for haunt actors in my posted video, The Mummy's Tomb.)

Oh, well, there's always next year. As they say, never send a boy to do a man's work.  Thanks for all your help!