I have had a Roku box for years..works great. I would also look at Amazon’s Firestick...we also bought one for another TV. This works great too. For a bit more money you can get Apple TV... works great, but does not allow access to Amazon movies. Nice for streaming any videos you might have on an Apple device
Actually I have been keeping an eye on Apple TV. It was $99. Now the price has dropped to $69. This is comparable to the middle tier Roku device (Roku II). Roku in addition to having the stick has three tiers of devices. My neice enjoys the top tier as she plays Angry Birds on it with the Roku remote. And speaking of the remotes, I hate the remotes but they did keep it simple.
Apple TV is just another device like Roku. Chromecast hasn’t come with a set top box, they have always been a stick which Roku has since copied.
If you do go with Roku, make sure you check out their channels on their website as there are many more channels on the website than on the device. There are even hidden channels on the Roku that is only found on the website. Some of these are adult in nature and are hidden from the youngsters. However if you do subscribe to a hidden channel, it is not hidden on your Roku if you subscribe to it. All channels/apps whether they are paid for are free are considered to be subscription based and can be canceled (removed) at anytime.
A subscription does not always mean you pay for the channel/app.It just means you want to have that channel/app on the list of your channels.
I have a very early Roku that I still use. It is the one where the channels scroll horizontally. I have been looking to upgrade after about 6 or seven years of using the current one I have.