New puppies and a new baby are easier than new puppies and toddlers but are by no means an easy match.
You need to think about walks - would you manage with a pram? Have the energy after a sleepless night?
Training classes - would you be able to get a sitter? How would manage training during the day with a young baby?
By 6 months she could be crawling - how would you cope with toilet training and a crawling baby?
Cost - babies are expensive as are puppies.
A boxer is likely to be a lively pup right into adolesence and beyond - how would you feel about an over exuberant Boxer knocking your newly walking infant off her feet? (it will happen)
Chewed toys?
Another option would be to try and get a rescue involved with rehoming of them if your Dad would go for that? I'm guessing not, since he'd be after the cash 
I can understand you want to rescue one, but it won't be easy. I've been there and done it myself. To be honest, I had PND and my puppy was what got me through it, but even with that it was a struggle.
The best thing you can do is try and help your Dad sell the puppies responsibly and not to the first tom, dick or harry that offers the right amount of money. Rescue involvement is the best option.