IMO you only need a cargo bike (i.e. long-tail or box bike) if you’re trying to carry more than one kid. Otherwise, a regular-size bike with a heavy-duty integrated rack should be plenty. They even make some that can carry a lot of weight and fold for easy storage (e.g. this one).
If you occasionally need to carry a lot, cargo trailers are a thing.
IMO you only need a cargo bike (i.e. long-tail or box bike) if you’re trying to carry more than one kid. Otherwise, a regular-size bike with a heavy-duty integrated rack should be plenty. They even make some that can carry a lot of weight and fold for easy storage (e.g. this one).
If you occasionally need to carry a lot, cargo trailers are a thing.