Adopting nieces

We live in maryland, my sister in law wants us to adopt her twins due February 20th but expected in January. She lives in Arizona. My husband is in the military if that pertains to anything. Anyway, we need to know the easiest course of action so we can bring them home straight from the hospital, or soon there after. Would guardianship be easier to do until we get them home and they are living here with us. Could we then file with just this state and cut the paperwork and expenses in half. We don't want to miss out on all the bonding that happens right after birth and my sister in law doesn't want to take them home from the hospital. She has already signed a paper with the hospital alowing us to leave with them and giving us all the visiting rights she has while they are in the hospital. She returns that to the hopital with the papers she fills out when she goes in to have them.
Bobbi