Your example of praise sounds pretty darn good to me! Maybe explain to mom that you are not only praising her child when she takes the initiative to do something on her own but you are using it as a teaching tool for the other children. The other children hear what is said to their friends and when they hear you give such praise to a child they are more likely to do the same...and this is indeed the point of group care!

There is also a good chance you are acting a bit out of character when a parent sticks around so long at drop off! It puts you in the spot light and it is not uncommon to get a tad nervous and end up 'over selling' yourself!!