In WandaVision, Wanda Maximoff used her reality-warping powers to create the perfect family, including two children. At the end of the series, she was forced to give them up.
In Multiverse of Madness Wanda tried to cross the multiverse into a universe where her children still existed.
Was it ever confirmed in canon why she didn't recreate them instead?
As said in comment by Paulie_D: Wanda could have never really recreated her children in that universe. She could have recreated the hex but then her children would never be "real" but always a construct of her magic as per her time in Westview. She could not have borne or suppressed this truth.
Regarding other universes: In some (a lot?) of them Vision had not been killed by Thanos. In these universes the children are real: they are not created by a hex but a result of natural procreation. That's why she went for the other universes rather then recreating the hex.
There is one question that also comes up when thinking about this scenario:
In all that universes there must be at least one where Wanda herself is dead but her children are alive and probably even Vision. Why didn't she select one of these universes?
The answer to that question is: Because there she would not have a version of herself to Dreamwalk to... and without the powers of America Chavez she would not have been able to reach her children there...
