Volunteering

Hello
My sister and I will be travelling to Vietnam in mid August to Saigon from Cambodia. We are looking for schools, orphanages and charities on the area that would appreciate some volunteering and free gifts and donations for the children. We would also love the opportunity to teach English. This is what we are doing in Cambodia and would love to extend our charity to Vietnam. We would not need accommodation and only a day in anywhere would be great! We are on a tight budget and not on Vietnam for long so would like somewhere we could volunteer for free bug give donations to the children in form of gifts and equipment that they need.
Please contact me with suggestions of places
Many thanks