I am thinking only one will work and while it's active within the Hamlet 

Hello  , 

Lord Redo, you can send 3 champions...but the game will considerate just the strongest one !

Yep as said above only the strongest one will apply, and only while it's in the hamlet.  Be careful though if you pull it out before the hamlet collection is completed sometimes the time resets to what it would be if the champ had never been there.  

My advice? never keep your Headman champ in hamlet;i find better to send a Druid champ-hamlet defense champ and Spying champ-spy champ.I would send Headman only when i want to collect those ressources..there s no point to keep it in hamlet all that time .You can test this easy;when you attack a hamlet  send your Headman champ and see how much time will take to collect all ressources with him in hamlet.. let s say 16h for example.... than recall your champ.You ll need to wait few minutes and eventually to refresh the game than check the timer again .. it will show much more-that depends on your Headman level-.. lets say now 24h .So now you will know if you send your champ in 16h you will collect all ressources so you ll know exactly when to send your champ.. after 16h..not before..anytime in between 16h and 24h in this example i gave you.If you still have doubts just send your Headman once in a while.. wait few minutes -refresh the game than see how much time will be left if champ stays in hamlet  than call him back-now you know time left . In time you will know exactly after how much time you should send your Headman.. some players looks for timer i look for ressources left in hamlet . For example in a shappire hamlet i send my champ when i see less than 1884 shappires left inside... no matter if 50% boost is activated or not-if i see 1884 left i know i can clame all ressources-Headman maxed in my case...but that s just me.

From experience, this is not correct. 

Druid Champ + Spy Champ both work for you in the Hamlet. These two are not mutually exclusive.

LOL  is not correct !!

That is like the game works mate...

And for be clear : 

- if you send  3 druids...the game will consider the strongest one.

- if you send 3 spy ... the game will consider the strongest one .

-  if you send there 2 druids + 1Spy , the game will considerate the strongest druid and the spy.

-if you send 1 druid and +2 spy the game will considerate the druid + the strongest spy....

I hope is more clear since your first question was about sending multiple champions in a hamlet .

I wish you a good game and a good day !