Long car journey - would laptrays be safe?

[scrappydappydoo]

We've got a long car journey ahead (10 hrs gulp) am thinking of things to entertain dds aged 5 and 3 - we have in car dvd player but don't want them glued to it. We have these laptrays - you know the hard tray and then beanbag bottom they use these at home to draw and colour on and was thinking that they'd be good in the car too but mummy paranoia has set in about how safe these would be in a car if we stopped suddenly? What do people think and are there any alternatives??
(if it matters dd1 is in a highback back booster but dd2 is still in 5 point harness stage 1 seat)

bump - does anyone have an opinion?

There was a post similar a bit further down. I use a soft tray - it's got a foam base so not really great for serious coloring but the lip keeps toys & snacks in place and it has flaps with net pockets to hold a water bottle, books, etc.

For safety, you don't want hard plastic that won't crush in case of an accident.

Hope this helps.