Original is a B/W 40 + years old foto. Exposed in a frame without any covering.
Wanted to restore and not improve original.

Steps taken, more or less:
1- Scanned to 600 dpi, RGB.
2- Levels adjustment and cropped white frame and worst parts.
3- Ran a Dust and Scratches filter to get rid of paper cracks that resemble paper texture (they wouldn’t show in the red channel using the FFT method explained in a local tutorial to remove paper textures).
4- Healed and Cloned spots.
5- Converted back to B/W using Lab Mode and Lightness channel.
That’s about it.

I have a tough skin so feel free to hit hard.

The kid in the picture is my girlfriend’s brother and we plan to print it full size for his up coming birthday, any ideas to enhance it will be appreciated.

I’m Spanish speaking so please excuse my English.

I think you have done a wonderful job restoring this image. It was a great choice for a first restoration. The only things I would do in addition to what you have already done:

1. The photo's highlights seem a bit bright, you may want to lower them a little.

2. Run the image through a de-noising program (I use Neat Image, but you can also use Photoshop's built in filter or some other third party program).

3. Lastly slightly sharpen the image.

I did those three things to your finished photo. The result is subtle, but I think it finishes the photo (my opinion).

Thanks for taking the time and for your kind words.
I agree with you in those three things, will do them. Gonna take some time to learn about ways to do them and understand how the tools work and such, also will wait to see if others point me to some mistakes and stuff left out (just noticed the forehead has a semicircular line over-behind the kids left eye that I missed). I can clearly see the noise reduction impact on the image, in particular the face of the kid, and the highlights correction, but the sharpening impact is not that obvious to me (Which tool would you use to sharpen?), nevertheless yours looks a lot better. My high resolution version should look even better if I can get it right.
Again, thaks a lot!