How long should it take to heal for elderly (88years old) tooth extraction?

No exact answer: First, no presence of medical conditions, if any were mentioned. Secondly, no mention of infection, which tooth, easy or difficult extraction, etc. Basically, we have very little information to go on. Finally, what is meant by "healing"? Older individuals do tend to heal more slowly, but everything else being equal, there is no major difference in healing time. A few days to a few weeks?

Healing: Depends on age, intensity of the dental infection, length of time infection was present, degree of difficulty of the surgery, overall general health, and so many other factors. You will get the best answer to your question from the General Dentist or specialist Oral Surgeon that accomplishes the surgery, that's the person most familiar with the 88 year old's circumstances.