First I would like to say that, without taking a look at it's content, it seems a bit empty. You didn't use any colours, title and such. Of course, you don't have to and a suggestion can be great without it. But it helps, you can read
this for more information.
Now, to your suggestion!
Firstly, your suggestion aren't really worked out. You have a basic idea that seem nice ones but;
Tsunami Survival - You have 20 seconds to go to a safety place before a big tsunami hits you! You will fail if you touch the water in the tsunami.
How would the map be transformed? What are the safety places? And the tsunami, does it enter the arena gradually or in one sweep. If it's in one sweep, it just the same as dodge the arrows. Just higher blocks that you have to parcour to? Just walk on? If so, 20s feels way to long... All the other minigames are 5-15s long. So it might be too long.
I do have to say that the idea would be nice with a bit more though behind.
Zombie Slayers - You get a random kit or random items, use them to kill zombies around you! You'll fail if you get killed by a zombie, the players may not hit each other.
Again, it is an idea but not worked out! What kind of kits will you get? You have to make sure that all the kits ave fairly the same change of succeeding, you can't give a player a wooded sword and others a diamond! I also don't really like this idea too much... It doesn't feel to fit as a minerware game.
Could you also add a poll? With options for neither one of the two and both, so we can vote?
Kind regards
~Fesa