Of course it is difficult to advise you with any degree of certainty without seeing your property, but my general feeling on the subject is to leave your small creeks as they are. These feeder creeks naturally dry up in the summer and begin to flow once temperatures moderate and there is more rain. Any disruption to that system may affect more than you realize, especially for wildlife downstream. Enjoy your lake and enjoy your dry creekbed too; the later can be very attractive when planted with a variety of smaller native grasses at their edge.