You can be assured that it's a scam. Why would they want to suggest a UK travel agency?
If it's not a scam, then that family have completely no understanding of immigration law, so unlikely to be certified sponsors.
There is no way for an individual/family to have any influence on your immigration.
Please take a review of the UKBA webpage Working in the UK I'm sure it will help you understand just how difficult and regulated it is to enter UK legally for that kind of employment.
I would forget the routes you are currently following and switch to the established and legal routes, at least you'd be safe and not open to fraud/scamming.
Good luck with your job hunting
