Attack with 2 taunting elf?

[NeverEnding]

What happens if I attack with 2 taunting elf? Who decides what creature will block what taunting elf?

[Twanos]

your opponent will be required to block but since there are 2 creatures requiring the block on the the choice will fall to the opponent to decide which or both to block.

[NeverEnding]

And can I cast an instand (such as Giant Growth) after the opponent makes the decision which taunting elfs to block?

[seba1983]

yes