As of 1.1.3, there is no way you can use the
/give command to give already enchanted items as you can't edit the NBT tag.
However, you could connect the button to multiple command blocks. One of them would say
/give @p diamond_sword. The other ones would say
/enchant @p smite 2 and
/enchant @p knockback 2.
I’m assuming the ids you’ve given are for the Java Edition, because the ids for PE are different and id 19 in PE is power, which is not available on a sword. Smite on PE is 10 and knockback is 12. A list of all the ids can be found on the wiki.
/enchant commands won’t work if the player is not holding the dimaond sword.