I have a 3 and 4 year old. 4 year old is in nursery has special needs but is able to walk but he does things like sit on the floor and cries several times but not for long periods of time. The 3 year old likes to walk but cries within 10 mins saying his legs hurt. He walks with his legs and toes turned in. I'm not 100% sure if his legs really do hurt or if it's just that he does not want to walk.
At the moment I used a single buggy and a baby carrier on my back. I could carry on doing that but it is hard getting him on and off my back. Or I could buy a really cheap double buggy. I don't want to use a buggy board as I don't like the leaning over and cant fold the buggy with the board on it.