We normally give $100 to the massage girl here at the hotel. That's a bit over 30 massages. (Massage costs $10p/h hotel gets $7)
She's 71/2 mths pregnant at the moment so we will give her $300 when we leave. We tip her well after a massage as well. Just have to be a little bit sneaky with it so the hotel doesn't know.
Same with the ice cream lady we've known her for 10 years as well. We buy an ice cream from her everyday but don't take it, unless our little one wants it, but we pay her double. Going to her place tomorrow night for dinner. So to answer your Q no it's not offensive they're very grateful for any assistance they can get. They have to pay for school after primary school and most simply can't afford it so the kids are working at 12.