Krenko, Tin Street Kingpin

• WWizards of the Coast2019-05-03
  Official Ruling
  The tokens created by Krenko's triggered ability aren't attacking. Because all attackers are chosen at once, a token created this way can't attack, even if it gains haste.
• WWizards of the Coast2019-05-03
  Official Ruling
  If Krenko leaves the battlefield after its ability has triggered but before it resolves, you don't put a +1/+1 counter on it, but you do use its power as it last existed before it left the battlefield to determine how many Goblin tokens to create.

Rulings via Scryfall