In your settings.py:
EMAIL_BACKEND = "djcelery_email.backends.CeleryEmailBackend"
CELERY_EMAIL_BACKEND = "anymail.backends.sendgrid.EmailBackend" # your setting from before
Also, note that django-celery-email doesn't know about Anymail's extra sending options, like metadata, tags, template_id, envelope_sender, etc. If you use any of those, you'll need to let django-celery-email know about them in your settings:
CELERY_EMAIL_MESSAGE_EXTRA_ATTRIBUTES = ['metadata', 'tags'] # or whatever you use