I do a bit of home boarding and have done a fair bit of walking.
Walking can be fairly profitable, I charge £8 for a 90 minute walk and would walk up to six dogs at the same time, so the money is okay, but is very binding, obviously owners are totally reliant on you to turn up every day, which can be hard with young children.
You need to be quite good at being in charge of dogs if you are going to walk a few, though I have never had any problems, if you have some training experience it will help alot. In fact I think it probably essential.
Home boaring is a total labour of love imo, I have just two regular clients but one I probably have for 6-8 weeks out of the year, I have a small house and garden and a dog of my own so I wouldn't take more that one dog at a time. I usually charge £10 a day, though one of my two regulars is £12 as he is super high maintenance. It is handy pocket money for me, but no way to make a living.
Personally I wouldn't want to do day care or boarding with several dogs in my house as it would be mayhem, the first couple of days with just my dog and a boarder is just non-stop playing/chasing/humping and with another dog in the mix it would be crazy. I think to do several you need premises.
It is also a big commitment and can sometimes seem like a huge responsibility, having another persons dog is almost as bad as having someones baby
.
Also you would be in the same position as me as you would only be able to take dogs that are rock solid with both other dogs and children and even then you would have to be super careful with the kids, (your children are exactly the same ages as mine btw). Even when dogs are good with children, when they first come they are often stressed and the kids excited at having a newcomer, I have never had a problem but I do find it hard to get much else done. I would never leave my children alone with a boarder. I also always do a free afternooon 'test' to make sure everyone gets on.
Be prepared for the fact that quite alot of people want to home board their dog as it cannot be left ie suffers from some degree of seperation anxiety, this being the reason why they don't want it to go to kennels, I have had a fair bit of damage done by dogs while I have done the school run (takes 7 minutes).
Also be prepared for the fact that the client will quite possibly want the dog to sleep in you room, (this has been the case with all but one of all the dogs I have ever boarded) and in some cases (my high maintenance dog) in your bed! Though actually he sleeps in a basket now, but the clients don't know
they insist he won't sleep anywhere but a bed with a person in it.
All in all it is quite an upheaval, for the duration your house is often covered in hair and slobber and flying dogs.
Sorry for the huge ramble, hope some of it might be of use, feel free to ask anything specific 