The very short answer: No. Sorry. :-)
The longer answer ...
First, your question shows you already understand the basics of how WikiTree works regarding multiple marriages, etc. For those reading this question who don't:
As you recognize, you can enter either biological parents or step/adoptive parents as the mother and father for a person. The others can be linked in the bio/text section, but it's ones in the mother and father fields that will appear in the family tree.
Grandparents aren't recorded anywhere. Grandparents are, of course, the parents of the parents.
Siblings aren't recorded either. Siblings are other people who share one or both of the same parents.
Your profile, of course, can have your wife appear. The mother of your sons does not have to appear.
On your sons' profiles, their mother does need to appear if you want her parents to be their grandparents. However, this means their step-siblings won't appear unless they're your children. If they're just the children of your wife, they'll need to be linked from the bio/text section.