Doolittle
Think a lot more thought on your part is needed; its not that straight forward at all.
What skills do you exactly have?. You need marketable and readily transferable job based skills. How about volunteering in the UK instead to begin with and see how you get on?.
If you were for instance a skilled bricklayer, NCO, medically trained or have proper teaching qualifications then this idea might be more feasible. As for teaching, well you yourself would not want some unqualified person to educate your son so why is it seemingly ok to walk into some school in some far flung land to "help" some students with their English?. They do not need such "assistance". They want properly qualified staff.
If you are not qualified to do it in the UK, don't do it abroad
More responsible organisations, which offer placements that really enable volunteers to make a difference, will take time to find the right match. The organisation should want to find out about your skills and specialisms and spend time finding an appropriate role for you. It should feel more like applying for a job than booking a holiday.
I would forget this whole idea as it is really not feasible for you to do; as other people have pointed out westerners on volentourism schemes is a minefield of ethical problems. It takes jobs away from local people and the work the westerners provide is sub standard primarily because they do not have the right skills.
Its also going to be nigh on impossible doing any such scheme when you have your son to look after as well.