My ducklings- are they terrified or just silly?

I got some mallards duckling at the feed store when they were three or four days old. They are now a week old and I've been trying to get them used to me but they still run around like they're terrified. I have been able to reach in and pet the female a few times but generally this is what they do. If I stand outside their see through tub and talk to them they look up at me, peep, preen themselves, stretch, and seem generally unconcerned. But if I reach in they run like the wind- straight to the water for a drink. They do this over and over. If they were really scared they wouldn't run to have a drink of water.. Would they? I get the feeling this is probably a duck being a duck but I thought I'd ask.

They really don't like being held. When I just pick one up the other one SOS peeps. They are happier when they're held together but that's tough to do sometimes.

Also, at one week old, are there any treats I can give? If I give treats then I also need grit, true? I thought I could maybe sit in a pen with them and give treats but wasnt sure if they're old enough. Any advice would be greatly appreciated!

They are being Ducks!
I feed my Ducklings Dandilions, Tomatoes, Peas and chicken scratch as treats.
I provide them with grit at all times.
Once a day I give them a bowl of their regular food with a treat mixed in and add water to make a soup. They gobble it up.
Sit near your ducks and talk a lot! They will get used to your voice.
Mine love me from a distance. When they see me and hear my voice they quack and wiggle their bums!

TOO CUTE!