I am thinking c2c straight to Southend East from Upminster. Although this appears expensive from previous posts. We have no other choice as we live in Upminster.
Probably a last resort if I can't find a cheaper alternative.
I am on the same boat, my son has to do the same route. if you check the topic above your one 'discounted travel c2c etc' you will see that a lady put the fares for the c2c from Upminster to Southend.
I found out that there is very little difference between train and coach. At the beginning I was thinking strongly about coach but the point is that coach pick up kids from school at around 3.45 and they wouldn't have time to do any after school clubs, sports etc. while the train gives you this flexibility that they can make their own way when they want. My son loves doing sports and told me he wants to go by train so at least he can do his after school clubs. Of course that everyone has got its own interests. But considering that the little difference I will opt for the train unless there is a coach who picks up later, which is unlikely to happen.