Multi sig transaction with Mycelium

[joe1234]

Hello

we are contemplating about paying an infrastructure-builder/contractor in a developing country with Bitcoins (if accepted).
The idea is to have a local NGO check the work and if they are done properly, to sign the transaction (by that NGO).


We don't know how reliable this NGO is, and what would happen with our BTC's, if that NGO would lost it's private key...


Questions:

- Is for that purpose a lightweight multi-signature wallet required? Or could Mycelium be used with it's feature called "Secret Sharing Split Keys".

- How should a private key for a multi-sig transaction/address be handed over to the 3th party?


Any feedback is appreciated very much. Thank you!

Joe