I've collected all kind of guides and walkthroughs to help me get all the achievements in Super Adventure Box. I'm going to run through the complete SAB two or three times to make sure I get them all. For example, I have a playthrough where I cannot die, and I have another playthrough to get all the baubles, secret rooms and digsites.
I was wondering myself one thing though: Which achievements cannot be completed anymore when you enable Infantile Mode?
Best Answer
The only achievement that I could not complete in Infantile Mode was "Scholar".
I am not sure which guides you are using but the best one I have found is the one from Dulfy.net which has everything collected together.
It also confirms that 'Scholar' cannot be completed in Infantile Mode.
http://dulfy.net/2013/04/01/gw2-super-adventure-box-guide/