I would like to set up a guaranteed purchase mechanism for BitCheques (a sealed tradeable "paper" wallet) with a 2 of 3 multisig and, if necessary, an escrowed smart contract with the arbitration mechanism built in.

https://bitcointalk.org/index.php?topic=5399679.0

How can I set this up so that a secure guaranteed purchase can be made from my website? The BitCheques will come blank, and will be guaranteed and/or insured up to a certain amount and for a specified time period.