It has a battery like any child’s toy that you would not allow a child to use on Shabbos and therefor it is NOT permitted on shabbos.
Or your wristwatch, which you would never wear on shabbos.
Batteries do not make items “Muktza”.
Furthermore, it is possible that texting is “only” Midirabannan.
Other then that, I will Echo WIY. When children are pushed to only learn or do chessed on shabbos, they dread shabbos, instead of having a day where the parents are home and spend time with their children (playing games, learning, but most critical, having fun). Or even just take a nap and relax from the stresses of the week.