you were told wrong
go directly to the priest, today. Your child should be baptized the same time you are. You will receive baptism, confirmation and first communion at Easter. She will receive baptism only (as would any child under age 7)
requirements for baptismal godparent or confirmation sponsor are the same for both of you
this person must be a fully initiated Catholic adult, living in conformity with Catholic teaching, including Church laws on marriage.
Must be at least 16 (18 in some places), baptized, confirmed and made first communion, not the parent of the candidate, not under any canonical ban from serving, willing to learn, understand and accept the duties of godparent–to assist the parents in the child’s Christian formation and education and model the Christian life–and if married, must be married in confirmity with Church law. Only one is required, but if there are two, must be one man and one woman.
the godparents you want must make arrangements to convalidate their marriage, including any preliminary steps, and to complete their Christian initiation. As it stands now, they have rejected the sacraments of the Church, so cannot until that is rectified, serve as a proper model and mentor for someone who is coming to the sacraments. It is quite likely that they desire and are willing to correct their situation, and only need guidance in how to do so. Please refer them to their own parish priest, or to the priest who is helping you prepare for sacraments.
If you are already baptized, and coming into full communion with the Catholic Church at Easter, your children including the baby are brought in the same time as you are, which means she would be baptized at the same time. Please see the priest today.
there is nothing in your situation that cannot be rectified, probably without as much difficulty as anticipated. true, you may have to find other godparents for Easter, but your family will be well on the way to reconciling with the Church and open to the immense graces Jesus has in store for them.
I would certainly not delay your own sacramental initiation, or your daughters, but use this grace-filled occasion and golden moment to help your step-mother return to full participation in the sacraments–how she must miss the Eucharist, God bless her. and who knows, with all of you praying for your father, great things can happen.