Being too laid back and hands off can give your children the impression that you don't care, or aren't interested, or that it's not important.
I suggest that you:
Tell them that if there's a subject they're struggling with, or a particular piece of homework, that you'll help them if it's in a subject you can, or you'll help them find resources on the net and work through it with them.
Ask in a neutral way what grades they got. Praise but not too much ('well done, you worked hard' rather than buying them a new bike!!) when they've done well. If they haven't, ask them how they feel about that. If they're upset, ask them if there's anything you can do to help (see above). If they're not upset, because they're not interested in the subject or know they didn't put any effort into it, acknowledge what they've said and let it go.
Make sure they have somewhere quiet to study, where they won't be constantly interrupted.
When they get to an appropriate age ( I suggest 13, before they start GCSEs), start talking in general terms about what they're interested in, and use that as a starting point for the following years to gently introduce the idea of thinking about their future and what they want to do as a job/career. It'll plant the seed in their mind to start thinking about it for themselves. Don't judge. Don't tell them that they can't because they're not good enough at maths/languages, just not bright enough, or whatever. Again be supportive. But help them to realise for themselves that achieving their aim will need hard work and effort.
I hope these ideas help you find your middle way. In summary, let them do it for themselves, but show them that you're interested and will support them.