A couple of points; I have seen holdouts in other scenarios end up with a second offer down the road at a premium to first offer but usually after a period of time.
AVB share price under the scenario you paint (50-89% OZL ownership) could go down, could become less liquid but may well not. AVB share holders would be de-risked to some degree by having a big brother. Though it is possible they could also get diluted in any funding deal.
A lot of permutations for people to think about which is why I'm counselling take your time.
AVB Price at posting:
15.8¢ Sentiment: Buy Disclosure: Held