Here's how it would work: You decide how many different friends and family you are going to send your secret message to, and how many of them will need to agree to unlock the message together. Let's say you pick 15 recipients and 8 need to agree. Then ANY 8 of the 15 messages can be combined to decrypt the secret.

No 3rd party service needed at all.

Couldn't you encrypt the results again with different numbers? So you could do interesting things like 'my wife AND (any 3 of 50 others)'