Let's try the standard scaling.

The aspect ratio is lost. The balloon looks bloated.

Let's try the same with Liquid Rescale.

The balloon is weird, there are still distortions in the features. We need to protect them.

We need to create a protection layer.

Let's select the balloon with the Foreground Select tool.

We draw an approximative selection around the balloon.

and paint over the foreground object. (note, this is a tool independent from the liquid rescale plugin).

A few adjustments are still needed.

Let's mark the balloon in the protection layer. The marking doesn't have to be perfect in this case.

We use a plain colour to protect the balloon.

The protection covers the balloon. Let's add other features to protect: the spectators

We tell the plugin that we have a protection layer.

This takes a few seconds...

... and now it's done.

We can hide the protection layer.

The balloon shape hasn't been distorted. Space has been taken in less important part of the picture.

You can not really find scaling artefacts with the naked eye.