Now I have NOT biked with a child of that age, but I have seen others do it AND traveled with children on long hiking trips. On long trips you can NOT be the only person on the trip who is tried, so must be the children.
After 60 miles, you will be tired, but the child, riding in a trailer, would have slept or other wised rested during the bike ride. Once you camp, you will be chasing after her, for she will be fresh and ready to go while you are tired do to the bike rid. This situation will doom most trips.
I recommend you do two things, first get the child to "Bike" with you AND have a trailer (This assuming a pre-school age child). This is possible if you go with the child's mother OR some one else (The more Adults the better). One parent can haul the trailer for the Child to ride in when the child is tired, the other can haul a tag along bike for the child to ride and peddle as you peddle. This will tire out the child on the trip so both you and the child will be tired when it comes time to camp.
If the child is capable of riding their own bike, you should leave them do so. This will slow you down, but tire out the children. When the Child is tired, put the child in a trailer and the bike on top of the trailer (Make sure your trailer can haul BOTH Child and bike or have two trailers, one for the child and one for the bike).
If the child is school age (The above assumes pre-school age child since all you mentioned was you have been biking with the child since she was six months old), then the child can ride their bike the distance with you on an age/size appropriate bike and the trailer can be disbursed with (Or used to haul camping and other gear). Grade school age children will slow you down more then pre-school for the children will no longer be willing to ride in a "Kiddie" trailer or tag a long, but will insist on making the trip themselves. The problem will be the children will still be quite small and NOT capable of keeping up with you, thus you have to slow down to match their speed, but that is one of the cost of going with children.
Side note: Some people do NOT use a tag a long but a two seat tandem. The second seat is adjusted for the child, often with add ons on the peddle so the child can reach the peddle. This has the advantage of being able to use one bike, the trailer can be attached to the tandem. The down side is Tandems cost MUCH more then regular bikes, AND you will end up with a monster bike, a tandem followed by a Trailer. The biggest draw back is how does the child get on the seat? When people mount a tandem, the Captain (The person with the steering handle bar) MUST mount first and then hold the bike steady for the second person to mount. If the Child is to small to reach the peddles, the child will have to be put on and taken off the tandem by a third person. Thus you still have to have someone with you other then the Child.
My recommendation is to go with someone else, one with a trailer to take the child when the child is tired, and the other with an tag a long extension. Such tag a longs are NOT that expensive and you get to tire out the child AND will not lose that mush speed do to the inability of the child to keep up.
The big problem will be when the child reaches school age, to old to ride in a trailer (or a tag a long) but to small to keep up with you on their own bikes. You will be frustrated but if you work together with other adults not a major problem, but you have to bike in a larger group then by yourself and your daughter.
Here is one system to convert an adult Tandem for use by a Young Child
http://www.sheldonbrown.com/tandkids.htmlSheldon Harris other articles on biking with Children:
http://www.sheldonbrown.com/family/index.htmlOther writers on this Subject:
http://www.gtgtandems.com/tech/triplet.htmlPicture of what I call a "Tag a long":