My son is planning a week's trek in Georgia.
We googled a little and realized there are many routes and kind of hard to decide.
Anyone has been there?

Just an FYI -- Georgia (the country) topics are on the Asia Forum. Your thread may be moved over there.

Moved to the Asia Forum.

You probably need a specialized guidebook or site. My very dated Lonely Planet recommends "Walking in the Caucasus: Georgia" by Peter Nasmyth

I went to Georgia specifically to go to the Svaneti region. It was heaven. Although this is a remote region, it is surprisingly easy to access since there are dirt cheap flights from Tbilisi to Mestia, a fairly low key ski resort.

However, I am not familiar with all the possibilities for trekking or if everyone agrees on what that entails. Ushguli is the famous village to visit, and it is actually four small villages along a river. Many people choose to hike form Mestia to Ushguli, but I can't say that particular route seems worth it to me. There may be many other treks possible.

One area I considered but did not go, is the Tusheti. Access is blocked by snow most of the year. It too looks like a magical area to trek.

I did purchase a trekking map of the Georgian Caucases on the internet. It is published by Terra Quest and is 1:75000

I did hikes in Georgia and loved them. Do you have more precise questions?