1-If Baby is less than 3 months no need of visa. You can get visa on arrival. I also did the same for my baby when she was 75 days old. No problem at all.
2- You can register him on passport copy (if baby having separate copy) or mother RP / Passport copy. Also you can get baby RP within 2-3 days after that you can register him any where. But make sure that mother / father had already valid RP.