My past experience with worms has not been good.
I agree, there should be lots of viable cocoons. I suspect that if you gather as much of the castings as possible, it should come back to life. Looks like it will take 2 - 3 months before you are breeding again. However there should be enough little wrigglers for the kids to see. It might be fun for them to watch them grow from babies. I'd be sacrificing some avocado and rock melon slice to really get them going.
Quote: "There are no 'intermediate' stages ... just egg,miniature worms that are sexually mature in 2-3 months,and reach adult size in 1 year." https://au.answers.yahoo.com/question/index?qid=20090921060229AAXS9qp
We went on holidays over Christmas for 3 weeks and the girls who was supposed to look after our worms forgot to feed them and water them. I thought they had all died. Well to my surprise now after 2 months I can see more and more. So yes from experience I know they are still there.