If you're really serious about riding with your children there are a number of options available. Have a chat to your local retailer about these.
If you already own a bike then attaching one or two child seats is a good option. The traditional child seat attaches to a rear rack. There is also a front child seat option that places the child between the handlebars and your arms. These seats should be able to carry children up to the age of 3. Be careful not to kick your passenger in the head when getting on and off the bike. When the seat is fitted, practise with a 10kg bag of potatoes in the seat to help you get used to the balance.
Trailers can fit two children and well as toys, books, bags and all of your other bits and bobs. They also have the option of a roll cage, offer protection from the elements and keep your child closer to the ground. They are a bit harder to pedal uphill and you may not like not being able to keep an eye on your child.
This is an option for older children (4 and up) who are strong enough to hold on to the handles and not fall asleep while out and about. They usually attach to your seatpost. They’re great practice and children can feel like they are riding a real bike without worrying about veering off course.