Apparently there are a lot of opinions about the outcome of these quests. Apparently, if you free the tree spirit, the children are safe but the town & the Baron's wife suffer & the Baron hangs himself.
If you kill the tree spirit, the children get eaten, but the town is saved & the Baron takes his wife to a healer.
3. More people have positive outcomes if the "tree quest" is done before other related quests.

I most probably will kill the tree spirit to save the villagers & the Baron (although I haven't met him yet). But what if I free the spirit & not tell the villagers & the Crones about it (apparently there is that dialogue choice)? This might be a stupid question but would the fate of the Baron & his wife still be the same as if I freed the spirit and chose that dialogue tree when talking to Eaolderman & the Crones?

Either way, Kill the tree or not, The kids disappear and Gran goes nuts because she loses the kids. The best overall outcome is to kill the tree. Let's face it the tree is evil. Later when you return it will then effect the Baron and Gran

you free the spirit & not tell the Ealdorman & The Crones about it in the dialogues, would they still be angry at Gran and would everything then turn out the same way with the Baron hanging himself?

*Spoilers* When the Crones task you with killing the spirit locked away under The Great Willow, you have to kill it. If you free it, the Crones retaliate by cursing Anna - she's turned into a hag, and once you remove the curse, she dies. This, in turn, causes the Baron to hang himself back at Crow Perch. Kill the spirit under the Willow and you should be able to get the 'good' ending, where the Baron takes Anna away to be healed.

if you free the spirit & choose different dialogues when talking to Ealdorman & the Crones, the outcome would be the same as if you killed the spirit.

1. Kill the Tree spirit - children are dead, villagers are alive, Anna is crazy and Baron takes her away.
2. Free the Tree spirit - children are alive, villagers are dead, Anna and Baron are dead. Too bad
3. Hidden way: find and free the Tree spirit before talking to the Crones and the Ealdorman. Still, children are dead (because the Tree does not even promise to save them), villagers are dead, Anna and Baron are alive.

I think I will have to make choice 1, like I did it the first time I played it...

in order to recruit Dijkstra/Reuven, you need to infiltrate witch hunters' place w/o raising suspicion during the quest, Reuven's Treasure & asking Menge about the treasure. But even though I manage to not raise suspicion, when I ask Menge about the treasure & then about Dandelion, I get attacked. This probably means my cover's blown. So would Reuven help me? In order to remain "undetected" you can only ask about Dandelion but that would mean not asking about the treasure.

Sigi Reuven/Dijkstra wants me to Kill Radovid. I have to do five or six quests for him. Now I don't necessarily want to Kill Radovid. But not doing his quests would mean ditching a lot of experience points & also missing out a chance to meet Thaler who might give me 'Geralt' Gwent Card. Would it be possible to do Sigi's quests & choose not to Kill Radovid? I know Geralt won't be the one to kill him but I don't want Radovid dead.

Radovid is a bad guy and a little insane. He needs to die for a couple of reasons not the least of all it makes for a favorable ending. Your only choice is to refuse or participate. I chose to have him killed. There is a couple surprises in the quest as well

Thaler before I refuse Sigi Reuven?