Multiple approvers in workflow

I would like to get my workflow to send out approvals in serial mode to two approvers when the requisition is more than $xx (i.e.$5000). Can you help with that?

1. send approvals to immediate supervisors
2. escalate after 2 hours
3. send notification to requester when no approval was ever received. Is this possible?

 Please help me to modify the current WF. Any help would be appreciate.