Hip Hammock they would outgrow fast, How about one of the baby wearing slings such as a mei tai? (not the drink! lol) I have seen several people with them at zoos with 2+ year olds and they love them even at that age. They can be worn with baby in front or back. I'm going to use one with my new baby after they are born.
If you are handy with sewing or know someone who is they even have patterns for sewing available online. Here are some examples at the actaul site which has tons of color/pattern selections http://www.meitaibaby.com/gallery.html#
Here is a link to all different kinds of carriers and how to make them....
http://www.thebabywearer.com/lists/Sewing.htm
Good Luck!
C.