I never had any problems with the original Strahd or its more recent incarnation in 5ed. But then again, my players are mature adults so...
I can see that playing CoS with a younger audience might prove more disturbing than necessary. In fact, CoS would not be my choice with a younger audience. Late teens ok, but early teens or younger? No way.
Now with adults with sensitivity problems...
Vistany are fine as long as you do not portray them all as bad. Some are good, some are bad and some are trully corrupted. Have some good Vistani warn the player that some of them are working for the devil Strahd. When asked the question of whom, have them answer:" We do not know, that is why we tell you. We are as much victims as you are in this matter. If you kill the devil Strahd, we will be free. But until then, we are silenced if we want ro survive." This makes the majority of the Vistani victims of Strahd and not collaborators. This is how I have always done it.
For the children deaths...
Keep this. Keep the house, the hags. An horror story does not spare the children. In fact, saving them brings heroism to the fore. The players have a chance to save children and their very souls. Seeing the evil of the hags and fighting it can be very cathartic for people. They are adults, they can manage and understand that evil is evil. I would certainly keep this in the adventure.
For the mongrelmen...
This part of the adventure is reminiscent of the Dr Moreau's Island novel. The grotesque associated with that part of the adventure can be unsettling but again, I would keep them. Especially if you intend to portray the Abbot as the mad angel that he is. Again, the goal is to unsettle your players with maccabre, grotesque and madness. Being witness to that can push the adventure a bit further down a feeling of righteousness in fighting the evil in CoS.
But if you fear that CoS is too hard on your players, why play that adventure in the first place? With so many changes required, the adventure itself is no longer a Gothic horror but a simple hack and slash the vampire. At this point, so many modifications and/or omissions just don't justify playing it. I always agreed on the Vistani as I have never played them as one sided villains, but I acknknowledge (now, at least this forum opened my eyes on that) that it is an easy trap to fall into and modifying that is mandatory. But the rest? Unless you are playing with young children or young teens... I would change nothing.