I suggest that you contact a guardianship attorney where you live and ask about the appropriate place to file for guardianship. In most states, if you open a guardianship where the child lives and you want the child to move to another state, you need to open a guardianship in the new state and transfer the local guardianship. If that is the case where you live, it's probably best to open the guardianship in the county where your parents reside. Then, a transfer would be avoided.
But, do check with an attorney who practices guardianship law to make sure that you can avoid a transfer,if possible. it will save time and money. An alternative is to contact a guardianship attorney in the county where your parents live and ask the same question - then see what will work out best for you.
I concur with my colleague and strongly recommend that you contact an experienced family lawyer in the jurisdiction, where the child resides. However, as a preliminary matter, what is the father's position on this issue? Is he in agreement? If so, you may be able to enter a Consent Order setting forth the terms of your agreement. Once you speak with a family lawyer in your state, issues relating to jurisdiction, timing of filing, etc., can be worked out in a way that is designed to expedite the process for you and your family.
Best of luck.
This response is only intended for informational purposes and is not intended as legal advice or as a substitute for hiring an attorney in your state. Further, by sharing this information, it is in no way intended to establish an attorney client relationship with the reader.