I seem to be obsessed with the amount of sleep my DDs have ....

[sandyballs]

.... I know its the summer holidays and they don't need to get up for nursery (they're 4.5) so I should really relax about it a bit, it's no big deal if they go to bed a bit later. But I find myself getting anxious from about 7.30/8.00, mentally working out how many hours sleep they will get if they go to bed any later. My DH thinks I'm nuts. Does everyone else relax their bedtime routines in the holidays?

personally, I like routine to be continuous.

If by going to bed later means they wake up later then don't worry. If they wake up at usual time then I would suggest only putting them to bed late on occasion. However you know whats best for your darlings, if they have less sleep and are grouchy all day then you know they need more sleep, if no change at all then fine.