I'd be curious to know how they chose what order to offer revised schedules? If they did it by seniority, then they didn't retaliate. If they did it by salary, they didn't retaliate....etc....If they had a solid business reason for going in the order that they did, then it wouldn't be retaliation. If they used your FMLA status as part of the decision, then it is a problem and very possibly retaliation.
Was it a new business decision to have workers on Saturday? Were others who are not on FMLA and were not currently working on Saturdays required to now work on Saturdays and also possibly have childcare issues? Were other workers negatively affected? If so, then it would be harder to argue retaliation.
You would need to be able to prove that the ONLY reason you were given the "bad" schedule was because you are on intermittent FMLA. And that can be hard to prove. Especially since they DID revise your schedule originally at your request.
I do think that you have the right to use FMLA to protect your job for you needing intermittent FMLA time on Saturdays (not for child care but for medical care of your child) until your FMLA time is exhausted.

