In reply to Caralynh:
When our daughter was 18 months -2 years old, we did 2 things. Cut an old but good full sized bag in half and sewed it together and it worked a treat.
We also used an old tog 12 single quilt, laid her down, cut to size so as not to restrict and made a sleeping bag out of that which worked better (ie kept her warmer) than the sleeping bag idea.
Hope this helps, happy camping :0)