So they are only Advising not to hit a GA or Comercial?
Who said anything about hitting a plane? Why don't you read the advisory instead of making idotic statements?
In fact here it is.
http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/1acfc3f689769a56862569e70077c9cc/$FILE/ATTBJMAC/ac91-57.pdf
Read the first part about voluntary compliance.
BTW. How are free flight aircraft to comply with this? Should the FAA fine or jail each kid who loses their ballon?