Disposal of human waste

Sorry for the asking this question, but it is the reality for parents with kids . Our class B has no toilet (removed by previous owner) so we purchased a portable toilet . It has zip bags which you can tightly zip the bag and dispose it after you are done. We only allow the kids to use it in case of an emergency . I understand the law does not allow to dispose human waste in water stream , but can you throw it in the park's trash bin ? I feel guilty for putting in the the trash container because I witnessed many times that homeless people find things in the public trash cans (in downtown LA where I work, some homeless people even dig through the trash bins for foods)

How do you handle this ?

thanks