Patagonia travel: Nikon 18-55 + 55-300 or a (cheap) superzoom?

Hi all,

In a couple of week I'll start a trip in Argentina: Buenos Aires, Iguazù falls, and a nice tour in Patagonia.

I've a Nikon d3100 with the Nikon kit lens 18-55 VR and I'm thinking to buy a new zoom lens in order to take better pictures of penguins and whales
Due to my budget, actually I'm evaluating:

Nikon 55-300
Sigma 18-250
Tamron 18-270

I'd like to have some advice form anyone of you as made a similar travel...

It's better to have a bit faster lens like the nikon but at the cost of often changing form two lens or use a just a superzoom, avoiding any lens change?

Many many thanks in advance,
Harry