jazzDESIGNED - I will only post about this once since others have expressed similar thoughts to you directly & in the countless "What's a good first amp to build?" threads that you should find & read. Please repay my effort in expressing this guidance by reading this post & taking time to contemplate it.
You need to consider the impact, for you & your father & any helpers here, if one mistake is made/something goes wrong and one or more of your boards fail to come up. A single faulty or misplaced part, a single cold solder joint, a single solder bridge, a single error in the PCB fab (rare but it happens) could take down the whole project. The initial disappointment could turn into long-term discouragement when you found out how difficult the more complex designs are to debug.
The experience would turn from a positive one into a reason not to attempt anything like this again.
Posts like this that you may see as discouraging are actually well-intentioned ones trying to assist you on the road to becoming a happy contributing member of this community.
If you have the funds to attempt this project with little or no reservation, then consider a more approachable project. There is a continuum of DIY designs, complexity/likelihood-of-success wise, available to choose from (& sell it down the road if need be). E.g. looking @ amb's site offerings, the CK²III makes an excellent medium-complexity, great-sounding project... The M³ an ambitious reach as a first amp. A full-blown 4-channel β22 more a foolish choice as a first amp.