Hi tinkybelle,
whilst I understand you being surprised and did not really like the spraying, as mentioned before this is a standard procedure -especially in malaria areas- in order to offer better protection of the guests.
Nobody likes to be sprayed on -I actually did not like the spraying when having flown to Australia- but I believe it is nothing really to complain big time about. Yes, you should have been made more aware... Maybee it was written on the check-in form or so and you just didn't read it, I do not know and I am far away from trying to protect Starwood. But I am sure the excellent stay for the rest was well worth your time and your vacation was not completely ruined....
Whilst you mention that your husband had a skin irritation, it can be that he just had a allergic reaction which can occur with pretty much any substance (I for example am allergic to cat hair, even in minimal amounts)...
Anyhow, I think it is a valueable lesson learned, but since it appears that you were in an area where spraying is standard procedure, it is what it is. What kind of 'compensation' would you ask for... I personally think it is rediculous!
BTW: I will not reveal my next vacation stay, afraid of you spraying on me