Email Reminder after 10 days if the Opportunity owner does not create a new opportunity

Can we achieve it either by Workflow or Trigger?

If possible please give me sujestions?

Thanks and Regards,

Praveen.

Like:

list<library__c> lib_list=[select ID,Name,fee__c,(select ID,Name,type__c,(select ID,name,phone__c from student__r) from sports__r) from library__c];

Can it be possible?

list<account> acc_list=[select Id,name,Industry,Rating,(select ID,firstname,lastname
from account.contacts) from account where phone='abc122'];
system.debug(acc_list);
for(account a:acc_list)
{
system.debug(contacts.firstname);    // ERROR: Field doesnt exists
}

please help me from end to end discussion