No, you cannot do that, because "subqueries may be used in the WHERE or HAVING clause" (from spec).
Besides, the constructor must get only single_values_path_expression. Excerpt from the specification:
select_clause ::= SELECT [DISTINCT] select_item {, select_item}*
select_item ::= select_expression [ [AS] result_variable]
select_expression ::=
single_valued_path_expression |
scalar_expression |
aggregate_expression |
identification_variable |
OBJECT(identification_variable) |
constructor_expression
constructor_expression ::=
NEW constructor_name ( constructor_item {, constructor_item}* )
constructor_item ::=
single_valued_path_expression |
scalar_expression |
aggregate_expression |
identification_variable
aggregate_expression ::=
{ AVG | MAX | MIN | SUM } ([DISTINCT] state_valued_path_expression) |
COUNT ([DISTINCT] identification_variable | state_valued_path_expression |
single_valued_object_path_expression) |
function_invocation
and I am not sure whether in new FatherDto(fat, childrenList)
childrenList is considered a path expression.