Looks like you made quite a few purchases for a gift... very generous.  Sounds like you bought the linear gear for this project. Is it and/or do you plan to make it more height adjustable (outside the router plunge capacity?... if that's what you are depending on).

I'd be interested on where you bought the linear gear (local???) and how much? Most sites I found didn't quote prices. I'm not mechanical enough to search by name... I depend on visual pictures.

Details/build of that leveling setup could be a good subject for a blog.
Alex, The linear bearings setup was a supposed local eBay warehouse 😁
The costs were reduced/refunded after some shipping damage and delivery issues. 
I originally mounted the router on top of the bearings on the rails but it was way too high so I had to make a “Z” attachment mount. It gives me nearly 50mm of working thickness. 
The base is 5/8” ply on a braced 4x2 frame and jolly heavy. 
On the “gift” suggestion, the young builder is giving me some of his time to convert a bifold door unit into a trifold door unit between our dining room & sunroom to accommodate the now larger family gatherings. 

Life’s Good, Enjoy Each New Day’s Blessings