Pets don't have to be expensive or a lot of work. Evaluate how busy your family is and take it from there. Your local pet store should be able to help you decide what is best for your family but make sure that if you purchase a pet, it is coming from a reputable organization.
With all that said, here are some pictures from L.'s house. L. takes care of the family dog with the loving guidance and support of his parents.
Dad puts one scoop of kibble into the bowl that L. holds up. When he is older, L. will be able to do the scooping all by himself.
L. then walks across the kitchen and places the bowl of food on the floor for the dog. Here, L. instructs a friend on the finer points of pet care.
Then they take the dog for a walk. Obviously, this may not be possible if the dog is young and untrained and I know from experience that cats & fish don't like going for walks. Finding ways to help the children do things for themselves may take some observation and thought but is well worth the effort.
A slow meander through the neighbourhood....
...then off for a little nature exploration once the job is done.