RE: Delegate approve to more than one person
As Manan said, there is no way to design one person have 2 delegater, and to define delegater of delegater is one of nice workaround.
I'm not sure if this matches your requirements, but you could use workflow user groups so that if one of the approver and delegaters approves it, it gets final approval.
I hope this helps you.
S.Kawamura