IMO if these are the current ages of the children then I would take another "girl". They grow so fast and by Aug Sept Oct your daughter should easily manage a 20 min. walk. I have little 2yr. old girls who have walked 40 min. with me, just for pleasure. Not at a fast pace. Just right for them. I have one boy and the rest girls right now and would rather another girl than boy. One boy makes it lonely for them as they get older and know the difference. On the other hand the dynamics of the group can change and you could end up with 2 or three boys. It all depends on the demand for daycare in your area. Is it pretty consistent or are there highs and lows?