I have tried Opera but didn't think it was any better than the Android browser. I have to remember that this is for the older in-laws to casually use so too many browsers might be a bit confusing.
I downloaded an older version of the youtube app from here http://www.androiddrawer.com/476/download-youtube-3-5-5-app-apk/
I then had to allow installation of non Google-Play apps, then set the app to not auto-update (not sure how to do that for an individual app so I've done it globally). Go into downloads and install the downloaded apk file and it overwrites the newer YouTube app. Then it's done. Don't forget to switch the security back to only allow from Google Play if necessary.
One thing I find odd is that there's no address book, contacts, people app etc. What's a good app to use with Google Contacts with syncing etc.?