Firstly - what you are suggesting is completely fair and reasonable. Your children's phones are a privilege not a right. They may have the phone but you pay for them - and they wouldn't be able to use them if you didn't.
You are absolutely within your rights to limit usage. You are the parent - you set the rules. There are lots of reasons why children and teens need to be off their gadgets (as well as adults).
Your children will naturally say things like "well other kids get their phones at night etc etc) - kids would rather engage you in arguing than actually do the thing you are asking them to do.
Have a clear set of house rules - including about mobile phones. Stick them on the fridge so that everyone knows what they are. Set the expectation - when it comes time to turn their gadgets in (and I mean giving them to you not just switching them off) - set consequences for not doing as they're told.
If they won't give you their phones at the time you set, then there needs to be a natural consequence (not a punishment) - i.e. for every minute you refuse to give me your phone you lose an hour of phone time tomorrow etc. Be consistent. Don't engage in arguments.
DH needs to be on board. I would have a conversation with him about your worries about mobile phone usage. If he can't agree with you then at least he should respect you enough for you to give it a try. Maybe say to him - let's give this a try for a week and see how it works. Lay out exactly what you want to do and ask him to follow it.
There's a website called empowering parents and James Lehman who offer excellent advice about how to deal with exactly this kind of situation.
Good luck - it's a thankless task being a parent isn't it?