Why not have her jump rope every day? I would think it would be as effective as rebounding. Most 8 year girls...well okay, when I was 8, it was true...like jumping rope and that moves the lymphs. It may go away from that.
As for the Walmart brand of rebounder, I do not see why it is not as effective as Needak or a $200 rebounder. Mine was not that much, I do not know the exact price, due to it being a gift. Yet, I do know they (parents) would not have spent that on it. Also, this was bought Many years ago. I do not use it as much as would be good for me, except it is still effective.
I did begin using this week, a couple times. I am interested in seeing how it works out for me.