I don't know which model of Tivo you've got, but mine will stream Netflix and Amazon and Youtube, if you feed it an ethernet cable. Also, the Xbox 360 and the Playstation 3 game consoles are particularly good at streaming video from those services. Most of our Netflix and Amazon viewing is on the PS3 at our house.

Something to consider with these services: All of the services have UI's which aren't completely child-proofed, as far as I could tell. Your description of your brother-in-law's situation makes it sound like childproofing is needed. For instance, on the Amazon service, it's fairly easy to go into the menu of movies which cost an extra rental fee (i.e., they are not the ones which come free with the Prime subscription), and from there, it's fairly easy to select a movie for actual permanent DRM-purchase, which is even more pricey. So before committing to a device, you should research its parental controls, to make sure that it's possible to lock out monetary purchases on that device.

I haven't tried other video streamer boxes. There are several (some mentioned in this thread already), and I'm curious to know what the BBS gang has to say about their simplicity and ease of use. For instance, you would expect Apple TV to be easy to use, but does it stream Amazon Prime and does it have good parental controls? Those are the sorts of questions to ask.

The streaming video market is starting to settle out a bit, and I'm starting to notice that the "subscription" model streams (Netflix, Amazon Prime) are collecting mostly second-string videos and TV shows. The better, more modern variety of movies and TV shows are available on the per-unit-rent/own streaming services, such as our old pals Vudu, and the rent/own side of Amazon Prime. I've been particularly happy with the Vudu service lately, since I can use it on the PS3 and they seem to be getting all the good movies for rental.

By the way, use this web site to list what's available for streaming on which services:

http://www.canistream.it/

One caution with that site: If you don't turn on Adblock Plus before surfing to that site, you will be presented with an ad for a less-safe and less-reputable way to stream movies. I forget the name of the service, but it's shady as far as I can tell. The ad is designed to look like a "stream this movie now" button. If you see it, don't pick it. The canistreamit site is very useful to just look and see which of the streaming services a given movie is available on. Then you go to that streaming service on your own.

Obviously that's too much for your brother in law, but if he's asking for a particular movie, you could do that bit of research and set it up for him.