multimedia guides at Tower of London - any good?

[007alert]

I'm taking my 3 dc to the Tower of London next week and am booking my tickets online. I have the option of booking multimedia things for the visit. I think it would be nice to add a bit of a focus to our trip, but don't know if the dc will need one each, or whether we would be ok to share. It's all getting rather expensive paying for the whole thing and I don't want to add another £12 unnecessarily. Has anyone used these guides? Are they worth it? Should I get one for each of us? (btw, dc are 9, 7 and 5). Thanks.

We went to the ToL when mine were 10,8 and 6. we just bought a guide book when we were there as there was plenty to do and see. Handy tip is to give each child a notebook and pencil then get them to draw stuff or write down fascinating facts as they go round. we do this still with ours and it means that when we got to a stately home or museum that we are interested in they have something too so much so that we usually end up dragging them out! Much cheaper than £12 on interactive thingy.

Thank you. I can get carried away when just ticking boxes on the computer and often end up spending far more than I wanted.