T.F.
My daughter started the violin beginning in 6th grade and they were taught the Suzuki method. We went on to be in the highest level orchestra at Middle and High School levels.
We didn't know it but she has a knack for music and she can play songs by ear. My favorites are the ColdPlay songs she plays.
We did use private instruction throughout the years. My suggestion would be to speak with your current music teacher because they know the teachers in the upcoming levels who are tutors, etc.
I can't answer about the piano, we only did violin.
We did purcchase her violin at Dallas Strings in Allen, TX. They are very reliable, honest and great to work with. My understanding is that they also take care of the instrument rentals for Allen High school and some McKinney schools.
Good luck!