They have a selection of players in different languages, select the one you want. You can not take them home with you.
My daughter was 9 when she did the tour without any problems. If your 7 year old is handy with an MP3 player he shouldn't have any problems. He will walk around with his own player hitting play when he gets to each section. The sticks can also be paused and rewound/fast forwarded by each section.
There is an extensive gift shop, not sure is they sell a version of the tour to take home with you.