I can't help with ancestry, because I don't really use it, and only have a basic tree on there.
Have you got your trees on any other programme? I ask because you really need to keep your main tree and all the notes and any photographs on a programme on your computer. Then you can just update your tree on the pc and upload it to ancestry, or tribal pages is a good one for online.
There's lots of programmes around. You can download your tree from ancestry to it. And depending on which home programme you choose someone will be able to let you know how to combine them.
Also if you ever leave ancestry you won't be able to transer your photos and notes if you have any on there.