I am not qualified to answer your questions I'm afraid. As far as I can ascertain, the one who would probably know the answers to your questions and more I imagine is Jennyjoyce1, a descendant of Johns daughter Merab. She appears to have made an extensive study of historical data, particularly in relation to the Australian Wenbans. I know from birth registry that William Wenban, son of Mary Anne Odiam and William, was born in 1822 before they left for Aus so that is another child to add to your list.I believe the family arrived in aus year after John's family, so about 1839. I am no authority, so please don't take my word, ask the experts.frederick Myles is aslo very knowledgeable on the Aus links and peter Wenban the authority on the English Wenban lines. He would probably know most about Dinah and Thomas Wenban if you are keen to follow that line of investigation. Also there is a Wenban website put up by frederick myles wenban with contributions from peter Wenban,( if you havent found already), with much info on the 3 countries the Wenbans are busily populating... England, Aus and USA (google Wenban and you will find it easily).
Most of my information comes from secondary sources, so not as reliable as original sources. I can only contribute mainly what I learned as a child from my mother Lucia Wenban, youngest of William (1859-1919) and my Unle Boy(Percie) who began researching the family history back in the sixties. Hopefully this post will point you in right direction.