Volunteering request letter to a school where your child studying

Dear sir, My name is Anu John. I am the mother of Luke Sonu who is studying in grade five. I have been notified by my son that your school is looking for volunteers to travel for the science trip. As I am graduated in physical science, I believe I could do better to make this trip more effective for children. Presently, I am not working so I have enough time to do other activities. Hence, this would be a great opportunity for me to serve children in order to develop their interest towards science. Also, I thought that since I have such a long relationship with the school I would put myself forward. Previously I worked as a science teacher at an elementary school, but I had to quit my job in order to look after my son. I hope my job experience will be an extra advantage to connect with children easily. Considering the above reasons I think you would find me as a suitable candidate for this volunteering programme. I would be obliged to you if you could consider my request. Yours faithfully Anu