The real answer is to ask your tax preparer. Of course, if you're doing it yourself, then that's why you approach a forum. I see a couple of problems:
From pub 502:
Lodging
You can include in medical expenses the cost of meals and lodging at a hospital or similar institution if a principal reason for being there is to receive medical care. See Nursing Home , later.
You may be able to include in medical expenses the cost of lodging not provided in a hospital or similar institution. You can include the cost of such lodging while away from home if all of the following requirements are met.
The lodging is primarily for and essential to medical care.
The medical care is provided by a doctor in a licensed hospital or in a medical care facility related to, or the equivalent of, a licensed hospital.
The lodging isn't lavish or extravagant under the circumstances.
There is no significant element of personal pleasure, recreation, or vacation in the travel away from home.
So, a third days for touristy stuff is risky--it seems "significant".
Also, under transportation:
Transportation
You can include in medical expenses amounts paid for transportation primarily for, and essential to, medical care.
You can include:
Bus, taxi, train, or plane fares or ambulance service;
Transportation expenses of a parent who must go with a child who needs medical care;
Transportation expenses of a nurse or other person who can give injections, medications, or other treatment required by a patient who is traveling to get medical care and is unable to travel alone; and
Transportation expenses for regular visits to see a mentally ill dependent, if these visits are recommended as a part of treatment.
Every reference I see talks about a parent--single person, necessary co-traveller. Of course, there is no reference to multiple kids; no government document needs to handle all cases. But I would say you risk having this be a non-qualifying expense for...$300? Why not just expense what you can be confident in? Or, it could be worth the professional help not to jeopardize the whole thing.