As a Teacher of the Deaf, I really felt good reading your question.
Yes, you are correct, the Deaf community appreciates the hearing community learning about their culture and language. I have had some deaf teenagers mainstreamed in public high schools that felt isolated because their hearing peers failed to understand or even want to learn basic communication. The one district I work in has accepted and used ASL as a foreign language choice and provides this through distance learning which is taught by qualified ASL instructors. In my area, these are wonderful and positive changes....and the classes are always full!!
I also have a 4th (now 5th) grader that has been with his same peers since kindergarten...and most of his class (which entails almost 80 children dispersed in 4 different rooms) have learned either basic sign or have learned advanced sign language to communicate with my student. He has an interpreter that runs ASL classes after school,...open to any student...and her classes are packed daily with a total of 30 students on a crowded day. I see such a huge increase in the interest in learning sign language...and it's such a positive thing.
I do not see any negatives or disadvantages to teaching hearing children ASL.
Teacher of the Deaf for 4 years, signing for 5 years.