From what I can work out of the birth sequence, we have Joseph (1786), Mary (1790) in Hartburn, I have found a Ralph (May 1797), Felton, Ann and Dinah (1799), Felton, Richard (1802) and Alice (1804), Edlingham.
There is also a marriage of Joseph in 1812 in Edlingham, a witness being the elusive Thomas. Thomas isn't on IGI, so, a parish without good coverage is Longframlington, which sometimes has entries included in the mother church of Felton but sometimes not. Glantlees where George was working, is, if I remember correctly, in the Longframlington bit and there is a nice gap between Mary and Ralph.
Christine, if you do get to Woodhorn, then maybe it might be a good place to look.
Janet