is there a way to send a lot of items all at once to someone?

Not send, no. But you could set up a trade and have them offer junk on it, that way you can give them 10 items at a time, but it won't be much of a surprise if that's what you were going for :P

I actually just learned that they don't even have to offer anything on the lot... they can make an empty offer and it can still go through. It kind of blew my mind when someone suggested it to me the other day.

oh ok thats cool.