Am I doing enough?

[daycaremum]

I think you are doing fine. If you don't want to have structured activities or circle time you don't have to. Just as effective is discussion during free play with the children. They will learn through play. Count the number of blocks in their tower, point out the colours in a puzzle, ask them what they are cooking and what ingredients they used. Sing a song relevant to what they are playing with. Alphabet song when playing with letter magnets, Old MacDonald when playing with the barn. Often times I ask the kids what song they would like to sing and we sing whatever they come up with - impromptu. Read books to them during free play, if they want to sit and listen great, if they don't, that's fine they can still hear you as they play elsewhere.
Like I said, I think you're doing fine. Now if you WANT to do more, you can use google to find a plethora of information