Does it make sense to translate my bachelor's thesis?
Yes I would translate it.
Some pros:

It helps you demonstrate your capabilities in research;
It may help you demonstrate your knowledge of the subject matter in your field if relevant;
It demonstrates that you are oriented toward communicating the findings of your research, which is a graduate capability they are looking to develop anyway; and
It shows initiative.

Some cons:

Its too expensive to translate;
Its too technical to translate;
You think your application would be stronger without it!

These are the only cons I can think of...and my guess is based on what you have said that the pros definitely outweigh the cons :-)