Save in multiple tables in a single post - Django rest frameweok

I have 4 models:

class User(AbstractEmailUser):
    first_name = models.CharField(max_length=100, blank=True)
    last_name = models.CharField(max_length=100, blank=True)

class Event(models.Model):
    name = models.CharField(max_length=200)
    address = models.CharField(max_length=200)
    date = models.DateField()

class EventLocation(models.Model):
    event = models.ForeignKey(Event)
    ubigeo = ArrayField(models.CharField(max_length=200), blank=True)

class EventStaff(models.Model):
    recycler = models.ForeignKey(User)
    event = models.ForeignKey(Event)

Where what I want is to register an event and be able to assign users to this same post at the time of creation, assign users or not assign them if it is that he is not assigned. I have already created a nested serialier which in the documentation is well explained so that the event is saved and at the same time it is saved in the ubigeo field of the EventLocation table (district code of the place):

class EventLocationSerializer(serializers.ModelSerializer):

    class Meta:
        model = EventLocation
        fields = ('id', 'ubigeo')

class EventSerializer(serializers.ModelSerializer):
event_location = EventLocationSerializer(required=True, write_only=True)

def to_representation(self, instance):
    representation = super(EventSerializer, self).to_representation(instance)
    event_location = EventLocation.objects.filter(event=instance.id)
    if event_location:
        representation['event_location'] = event_location.values('ubigeo')[0]
    return representation

class Meta:
    model = Event
    fields = ('id', 'date', 'name', 'address', 'schedule', 'event_location')

def create(self, validated_data):
    location_data = validated_data.pop('event_location')
    event = Event.objects.create(**validated_data)
    EventLocation.objects.create(event=event, **location_data)
    return event

    def create(self, validated_data):
        location_data = validated_data.pop('eventlocation')
        event = Event.objects.create(**validated_data)
        EventLocation.objects.create(event=event, **location_data)
        return event

and it works correctly, but how would you add the users you want to assign to the event at the same time? I know I have to save them in the EventStaff table but how do I insert them in that same post?

This is my viewset

@transaction.atomic
    def create(self, request, *args, **kwargs):
        with transaction.atomic():
            try:  
                data = request.data
                serializer = EventSerializer(data=data)
                if serializer.is_valid(raise_exception=True):
                    serializer.save()
                    return Response({"status": True, "results": "Evento registrado correctamente"},
                                    status=status.HTTP_201_CREATED)
            except ValidationError as err:
                return Response({"status": False, "error_description": err.detail}, status=status.HTTP_400_BAD_REQUEST)

This is the format of the json that I command:

{
    "date": "2018-03-01",
    "name": "La prueba reciclaje",
    "address": "Av españa trujillo",
    "users": [
        {"id": 40, "first_name": "Raul"},
        {"id": 23, "first_name": "ALejandro"}
    ],
    "eventlocation": {
        "ubigeo": ["130101"]
    }
}