I'll be 100% honest. You mustmustmust have children's teachers who are Gifted. ie, gift of teaching form the HS. But not only this, the gift of teaching aimed at children. I know there's no "Gift of teaching those under 12" or something like that, but God obviously shapes us for specific tasks.
I can somehow- well, not somehow, it's obviously God working- take our theologically thin and rather boring curriculum, and the kids come alive. They're answering and asking good questions, remembering stuff from months ago, etc. This is the same exact curriculum that other teachers at my church do, yet they always complain how the kids won't pay attention, or how the kids are bored, how they don't respond in any way, etc.
(Again, it's %100 God, I'd never be able to do stuff like that, must be God using me)
So my point: there are lots of places to get curriculum. Type in Children's Church Curriculum at a good search engine and it'll be easy to sift through the crappy stuff and find the good stuff. BUT, I can't stress this enough, none of it will do the kids any good what-so-ever, if the teachers themselves are not actually gifted by God to teach children. I haven't been much help in pointing you to good curriculum, but again: the curriculum can be the best, but if it's not wielded by a teacher who actually has the gift of teaching, it'll do the kids no good. I know the objections churches give for being skimpy when it come to children's ministry, but I know God is stronger than any objection any church will give.
I can help in this little way: go to google and type in "top 100 children's ministry blogs", and your search will come back with, well, just that! There's a children's ministry that has a page with the "top 100 children's ministry blogs" ranked, form the last year (I think it has 2013, and 2015). I use it mostly to learn from, but most of those blogs have TONS of resources attached to them, including whole webpages and forums you can ask questions (like "Hey, anyone know of any good curriculum?"). But again. . .again. . .
None of this is a substitute for the Christians who God gives the gift of teaching to. Pray for them, God will send them.