I agree with what sleepy said, but noticing that she didn't really answer your question about noise, light and activity, I will say that they generally hide from bright light, so if you do get one, realize that you won't see it much during the day. As far as noise goes, mine doesn't seem to mind me playing loud videogames that include gunfire noises only a few feet from her enclosure, so the 11 month old crying and such probably won't be a big deal. Activity in the room isn't a huge big deal, as long as they're not being directly harassed. I frequently see mine watching me (don't get into a staring contest, you'll lose, they have no eyelids
).
Other points to consider: whether you get a crested or a leopard or some other type of lizard, if it's your first lizard, I would go with a healthy looking juvenile or adult rather than a baby. Babies need to be maintained more carefully, especially with regard to humidity. They have less mass, so it's easier for them to get dehydrated or undernourished, and especially with the cresteds, they're *tiny* (mine started out able to sit on a fingertip w/o really hanging anything off of said fingertip but her tail).
All that being said though, I agree with sleepy - while cresteds aren't too hard to take care of, they do require more maintenance than a leopard gecko and are less handleable due to their ability to stick to *anything* and their propensity for jumping. If our warnings about them being a bit harder to take care of don't dissuade you, then go into it knowing what you're getting into. They are very satisfying and interesting creatures to have around, and, imho at least, they're cute as can be, even including the fact that they poop everywhere
.
Whatever you decide to do, enjoy, and if you have to let go of the ball python, I hope you'll be able to find a good home for it.
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0.1 Albino Leopard Gecko - Tigger
0.1 Crested Gecko - Pooh-Bear