Hello,
I'm from Ukraine, Kiev.
I have a good experience in upgraded Joomla's sites from 2.5 to 3.x.
Some plugins from Joomla 2.5 not supporting by Joomla 3.x (actual version is 3.11), in this case I think we can find another plugins.
In any case, you able to see a new release on my or your hosting before changing your actual sites.
If you cooperate with me, you will be satisfied.
With best wishes,
Sergeo