With rubber bands "elastics", you can use them. I prefer on the base of the hair rather than the ends. However, cut off the rubberbands upon take down. The issue with putting it at the ends is that since the ends of the hair are quite fragile, it can break the ends of the hair. In addition, it makes it difficult to moisture the ends of the hair properly. With it being at the roots, it can also cause breakage if it is done too tightly and your child pulls on that area or itches that area. That is why some people experience short hair along these areas. This issue can also happens with hair ties too. It is your preference whether to use it or not.
To secure ends without rubber bands, I do this
How I remove rubber bands and get rid of lint at the root, do this
Stay beautiful! 💖