For Alice, you should get the new scene if you ask her to do doggy style in her room after you officially begin a relationship with her.
As for Maria, there's a bug in the current version. If you've used a transformation potion on her, it technically locks you out of the non-transformed version of the scene (it's essentially the same scene, just without the transformation). If you really want to get it for completion sake, you can talk to Rei (your fairy guide) and ask her to enable the content filter. That will let you get the normal version of the scene, and you can disable the content filter again when you're done.