Aah, thats what I like about this forum: its all warm, welcoming, encouraging, supportive, fluffy even.
So I'll just pop in the grumpy old pagan viewpoint. You want to walk into Santiago for Easter, so walk in Holy Week, when other than the festivals in July, its the busiest time of year on the last 100k or so of the caminos? You want to walk when available accommodation is under near maximum pressure and if not pre-booked already may leave you reliant on taking scratch or walking some extra km's at the end of a day?
You've not given us much to go on. How fit, how adaptable, how open to some pretty challenging exposures in crowded communal living your girls might be. But me, I wouldn't take two pre-teen girls into that environment without some experience or at least forewarned. My god-daughters in their time were pretty damn sure they didn't want to do any such thing even though, or perhaps because, most of their parents are Pilgs.
Happy planning and buen camino