Yeah Hadens do not come true to seed, but on the other hand, so many new varieties have come as a result from Haden seedlings. but the chances that any of these seedlings is better than cultivars already known is very slim.
I would also suggest either grafting with the mother Haden tree, ( If another Haden is what you want ) or Graft with some other variety, which is what I would do. so many great varieties to choose from, go for it !