It is worth considering the long term benefits to yourself, your local area and the whole planet. You may think that just by walking the children to school, rather than driving them you will not make much of a difference but actually it could make a huge long term difference.
Firstly consider the amount of pollution that you have been preventing by not driving. You may also have found that as you were more used to walking, you avoided driving at other times as well and so there is this add on too. Other parents may have seen you walking and decided to follow your example and other children too, so it could have had an influence there. Your children will also be I the habit of walking more and so may walk a lot more as they grow up and encourage their families to do the same. This can actually be very significant, more than you may have ever thought.
Health wise not using the car has many benefits. As well as those illnesses linked with pollution being reduced, you will also be fitter and healthier. The body needs exercise and by walking or cycling you will be getting more and benefitting from it. A thirty minute walk a day can extend lives by 2-9 years and it can also improve the quality of life by helping to keep illness at bay. Not only will it help you to keep your weight down but it will also help you to have a healthier heart and other organs too. If you have fewer illnesses then insurance is cheaper and you will miss less time off work due to sick leave. You may also be able to work longer into old age due to having better health.
The local area can get a big boost by less car use. If public transport, such as trains and buses are used more, then there will be more services provided by them which all of the community can benefit form. Roads will need less money paid for them and this could be used to improve other local areas. The air will be cleaner for everyone as well.
Less cars on the roads means less congestion. This means that people can get around more easily which will mean they are less stressed and less likely to have car accidents. It can make for a much better atmosphere locally if people are more relaxed and happier generally and if they are not getting worried about traffic jams this can be a factor in helping.
Setting an example to your peers, friends, family and children of using the car less can be great for the future. If they follow your example and do it as well it means that generations to come will also be thinking hard about whether they really want to be using their cars. This will mean that all of the advantages of not using a car so much will be passed on to many more people.