A few observations from an audiologist...
1. A 40 to 45dB hearing loss IS significant. Especially, for a school aged child. You should get appropriate recommendations from an audiologist, not an internet forum.
2. A CIC is inappropriate for a 70dB hearing loss. It would not offer enough power without significant feedback. Also, if you are still growing, a BTE is the only way to go. Otherwise, each time you hit a growth spurt you would have to buy a new hearing aid at $1500-$3000 each. If you have a BTE, you would only need to buy a new earmold at approx. $50 each.
3. The last place a hearing impaired person should be without hearing protection in an orchestra. You should really look into a pair of Musicians Earplugs in you are going to continue with music. The are made Westone. Look them up on the net or ask your audiologist for info.
4. Sign language is a fun language to learn but rather useless if you are not surrounded by others that use sign language. What, are you going to teach your skater buddies to sign?
5. Money should not be an issue. All states have programs to help pay for medical care and prosthetic devices for school aged persons. With your reported degree of hearing loss, hearing aids shouldn't be a choice but mandatory, at least in school.
If you have any other questions, let me know!
Jim