I teach Kindergarten and if I had a choice, I would just use manipulatives when teaching Math. First of all, I do not like the Math workbook that they have. The directions are hard to understand, so you can just imagine how difficult it would be for four and five year olds. Anyhow, these are their books and I have to use them. Plus, they will be going home at the end of the year and I do not want parents to see a lot of blank pages.
I believe at this age that children learn more by hands on activities and by using manipulatives such as blocks, cubes, etc. In fact, there are schools that do not use worksheets because they believe that learning should be all hands on at this age. I think there needs to be a balance though. I am very much for manipulatives and hands on activities, but I do not see anything wrong with using a worksheet for reinforcement.
When I teach Math, I do not start with the book. For example, a concept that we recently did was top, middle and bottom. You cannot assume that children automatically know where those positions are. Some may know, but some may not. I used colored blocks for this lesson. I took three colors and put one on the top, middle and bottom and I had them name the colors on each level.
Then I told them which three colors to get and told them which positions to place them in. They had fun with this and learned better than if they had just used the book. Then afterwards, we did a page in the Math workbook where they had to circle certain objects that were on the top, middle and bottom. Even if I did not do the workbook page with them, they would have learned the concept just by this hands on activity.
There are very important concepts to learn in Kindergarten Math that will prepare your students for the upper grades. You definitely want to teach them in ways that they will remember for a life time.