Hi Mike,
The context node that you are using is a mixed node, so from this node you need to get model node so that you can cast the entity into CL_CRM_BOL_ENTITY.
Here's the sample code:
DATA:
lr_mixed TYPE REF TO cl_bsp_wd_mixed_node,
lr_entity TYPE REF TO cl_crm_bol_entity,
lr_child TYPE REF TO cl_crm_bol_entity.
lr_mixed = me->typed_context->node_name->collection_wrapper->get_current( ).
lr_entity ?= lr_mixed->if_bsp_wd_ext_property_access~get_model_node( ).
lr_child ?= lr_entity->get_related_entities( ).