Children's Ministers usually fall into one of three categories. One category is that they aren't just children's ministers, but they're also student ministers or education directors and they're not really passionate about children's ministry anyway. The problem there is obvious so we'll skip that for now.
The other two categories are people who are great with kids or people who are leaders. Rarely can you find somebody who is both. When I say "great with kids" I mean somebody who would be a great teacher/communicator to kids, a great small group leader, etc. In other words, they're really good at doing children's ministry. They're great people to have around because they set the bar high and are naturally gifted in that way.
The problem is, they may not be leaders. They'll do a great job of getting a new or struggling children's ministry growing because of the excellence in what they do but all of that will only last until more people are needed in order for the ministry to grow. This is why churches should look for strong leaders when hiring children's ministers.
In most churches, the children's ministry is the largest volunteer team. In order to continue to grow and build that team you want a leader who can always take the team to the next level. They do that by developing leaders who lead other leaders. The create teams that they eventually step out of. They delegate responsibility and not just tasks. They invest heavily into a group of leaders.
Children's Ministers who are excellent at doing children's ministry are a great fit for large churches that can hire them. They'll help raise the bar of excellence and make sure that everybody is constantly thinking with the mind of a child during planning times. But, churches shouldn't make the mistake of hiring an excellent doer when they need an excellent leader.
In rare cases somebody is both, but that's far from the norm. I don't claim to be either but I'm working on the leader aspect because the best I can offer as a doer of children's ministry is that I can easily act like a 7 year old…….even when not required to.