the will has been on my site www.manxnotebook.com for some time. However I have doubts about your identification
(a) Jony would be 86 at time of death
(b) she was 16 years older than her husband - not a common occurance
(c) she had six living children - statistically unlikely at her age but only one grandchild is mentioned
(d) the phrase 'if the heir is under age' seems very strange
(e) one son was married (with a marriage contract) not long before the will was made

my own guess is that Alice was her eldest daughter with possibly two children (one being Alice the mentioned grandchild) - assume 25 as age of first birth then my guess is she was around 55 or less at time of will and that you have lost a generation