Mapping Json to ef6 ComplexType with ICollection but cannot cascade deletes

I have some complex JSON I am loading into directly into a model class but I want to ensure that if the root record is deleted the child records will be deleted too.

However, due to the fact I'm using a ComplexType I can't seem to get the syntax right.

The rest of the very large JSON piece is working, but the part represented by the simplified example below is not.

Sample Event JSON:

{"eventId":12345,
"zone": {
    "beach": {
        "score": 19,
        "team": [{
            "id": "abcdef",
            "name": "Barry",
            "playerType": 2
        },
        {
            "id": "bvfe43",
            "name": "Adam",
            "playerType": 1
        },
        {
            "id": "g3yh6",
            "name": "Mary",
            "playerType": 1
        }]
    },
    "cave": {
        "score": 1,
        "team": [{
            "id": "qPoavMkCTeKIy_htsvSKpQ",
            "name": "CAPITALMONCALAMARICRUISER",
            "playerType": 3
        },
        {
            "id": "ggsd84",
            "name": "Tibor",
            "playerType": 1
        },
        {
            "id": "2332edc",
            "name": "Jun",
            "playerType": 1
        },
        {
            "id": "f234fg54",
            "name": "Aaron",
            "playerType": 1
        }]
    }
}

Every Event has a zone.beach and a zone.cave, and both zone.beach and zone.cave had a score and a team.

My ef model is:

public class Event
{
    [Key]
    public int id { get; set; }
    public int eventId { get; set;}
    public Zone zone { get; set;}
}

[ComplexType]
public class Zone
{
    public Beach beach { get; set; }
    public Cave cave { get; set; }
}

[ComplexType]
public class Beach
{
    public int score { get; set; }
    public ICollection<Team> team { get; set; }
}

[ComplexType]
public class Cave
{
    public int score { get; set; }
    public ICollection<Team> team { get; set; }
}

public class Team
{
    [Key]
    public int teamId { get; set;}
    public string id { get; set;}
    public string name { get; set;}
    public int playerType { get; set;}
}

And I load the json like this:

var event = JsonConvert.DeserializeObject<Event>(content);

But when by database initializes with this code:

   protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Event>()
            .HasMany(a => a.zone.beach.team)
            .WithRequired()
            .WillCascadeOnDelete(true);
        modelBuilder.Entity<Event>()
            .HasMany(a => a.zone.cave.team)
            .WithRequired()
            .WillCascadeOnDelete(true);
    }

I get an exception:

System.InvalidOperationException HResult=0x80131509 Message=The expression 'a => a.zone.beach.team' is not a valid property expression. The expression should represent a property: C#: 't => t.MyProperty' VB.Net: 'Function(t) t.MyProperty'. Source=EntityFramework StackTrace: at System.Data.Entity.Utilities.ExpressionExtensions.GetSimplePropertyAccess(LambdaExpression propertyAccessExpression) at System.Data.Entity.ModelConfiguration.EntityTypeConfiguration1.HasMany[TTargetEntity](Expression1 navigationPropertyExpression)