well pretty soon they will need to to do homework, my eldest is at high school and most of his homework is set and done via the pc, ds2 is in yr5 and again tho they are given worksheets, there is homework to do via the pc, ds3 is in yr 2 and he also has a login for a specific page where he can do some extra stuff, mainly he still just gets sheets, spellings, reading but he has access to work from school via the pc.
its only in the last few years that we have got games consoles etc, when my kids were little we actually had 2 yrs without even a tv, but then i wanted to watch ER again and greys anatomy, desperate housewives etc etc 
we have a ds (one that is shared between the 3 older children) an xbox, a wii and a ps2, the ps2 was dps and the wii and the xbox were bought as family presents adn the older 3 children play on them together a lot of the time, plus the wii and the xbox with kinnect can actually be quite physical, today ds3 was doing a toy story game and was jumping up and down running on the spotm, flapping his arms like a bird, it was hilarious to watch and he was having a great time :)
but my boys also do sports, we have a climbing frame, a trampoline, bike to school everyday etc. its all about balance and everything in moderation.
we set limits for ds2 and ds3 as at 7 and 9yrs they easily lose track of the time and dont realise how long htey have been on a game. ds1 is 12 and pretty much self regulates, infact he rarely plays on the consoles at the moment, is more interested in his kindle and revising gcse bite size on the pc!
and even if your children dont SEE you using these devices, unless you hide them away i am pretty sure they will know of their existence and its pretty hypocritical to sit on the internet and not let your children on it at all!
the best option i have found with mine is to teach them to use it responsibly, if you never give them the chance to learn to do that then you are doing them a huge disservice ime.