My canon Lavellan drinks from the pool, because she believes an elf should take it if someone was going to, regardless of the consequences. It's also the kind of curiosity fueled thing she would do; her sense of self-preservation tends to fail in those situations, and in times when she wants to help someone or the world. Very likely the reason why she breaks her cover to run into the room where a shemlen holy lady is calling for help, which results in gaining a magic scar on her palm.
...This is probably why her clan kept her isolated in the wilderness for as long as they could. Well,anyway, I tend to prefer interesting over safe choices.
Agreed, for the most part. Centuries of elven knowledge would be lost if a human apostate with a track record of disappearing without a trace drank it.
As Lavellan can tell Morrigan: "It's my heritage."
I just did this quest tonight and decided to turn Cole more human...I felt bad after that. But when I took Cole to the restaraunt he seemed pretty happy so that made me feel a bit better.....still I'd rather let Cole stay a spirit it seems to fit him more. And the disapproval from Solas felt so heartbreaking. I always turn Cole into a spirit but I wanted to try the human path to see what happens in the future for Cole. 
I had no idea what to do for Cole's personal quest, and only had Solas' and Varric's advice to go off of. While Solas is a general spirit expert, Varric seemed to come from a place of personal understanding. He made a compelling argument that becoming more human is something that Cole wants, and mentioned how he's been there himself (his own brother and all). I thought, "How can I deny Cole something he truly wants because I think I know better?" So I very tentatively allowed Varric to help. I felt bad when Solas was angry, but felt like, "What's done is done."
I was still fretting about it when I took Cole out to lunch, but when he said, "Gentle. You watch me walk into darkness over and over, and you always worry. Thank you." I thought: D'AWWWWW!! Totally worth it!
(Even better, when he admits that part of the reason he was afraid of letting people remember him was because he was afraid of hurting or losing people, because he had equated "change" to "losing friends," but can now laugh with relief over how silly that was.)
The writers went to a lot of trouble to make it seem like there's no "right answer" to handling Cole's personal quest; it can really go either way and depend on what you personally think. That was just the reason my Lavellan chose to make him more human, and I chose to save instead of redoing his personal quest.
EDIT: I still felt bad over how Solas reacted, but oh well. Chalk it up to different parenting methods.