First of all welcome to the forum.
As talking about the speaker, for your 11-year-old daughter, I suggest you go for Vizio SB3621
. Known as the king of the budget soundbar, it has every feature, an 11-year kid would love.
Not only for kids but also it's perfectly fine for adults and costs only $106.5.
It is the best soundbar under $300 we have ever heard. he soundbar offers a decent selection of inputs including Bluetooth and will decode both Dolby and DTS. The soundbar and wireless sub feature excellent build quality and a seamless setup.