I took my 8 year old grand son on a hike last year. I would not advise trying to get your grand daughter to hike the entire trail. Make the hiking fun, not a chore. Take her on short hikes around Coleman and Pine Glen camp areas on the Pinhoti or the Chinnabee Silent Trail which is a spur off the Pinhoti..
There is no way I can give you specifics about how long it will take you. If you are happy with 10 mile days then 2 to 2 1/2 weeks is about right if you do not have to take a zero for resupply. I do not think there is any part of the Pinhoti that would tax you if you wanted to do 12 to 15 mile days. The other part of the equation is the daylight available. The winter days of 11 hour days versus the summer days of 13+ hour days will naturally impact your distance each day.
Go to the Pinhoti Trail Alliance page previously mentioned and to the
http://www.alabamatrail.org/hikingAL/ site which has trail descriptions and mountain profiles. These two sites give you plenty of information to compare to your experience to make a good hiking plan.
