Are you talking about 30 days total, or 30 actual days on the Camino itself? That being day one leaving SJPdP and day thirty happily walking into Santiago. No further walking to Finisterre (kinda anticlimactic, anyway IMHO).
Yeah, sounds like y'all could do it. Lot's of people do. My first Camino I carried a guidebook (non
Brierley ) that was based on walking the
Camino Frances from SJPdP to Santiago in 30 days. I deviated a bit from it because I had more time than 30 days, but it was plenty doable had I followed it exactly.
Since you have your children with you, you may want to leapfrog over a few places and hang-out a bit more in some of the cooler towns. Maybe an extra day in Santiago as well.