I do that all the time but because I fall in love with the next quilt I want to start. You may find that a boy will outgrow any quilt you make him, not just in size but his phases. You need to set this project aside and when you go back to it, it might look a whole lot better. Or, just finish it is what I would recommend because that you won't regret it in the long run but you will regret the wasted time and frustration. You can always use a old sheet or even go to a Thrift store and find a new one then you won't worry so much about cost. Save money there before you purchase fabric for the next one. Every quilt is a learning experience and setting the bar at finishing each one will prove a valuable tool. Beside, he is a boy! Give him one you don't care about then make him a nice one you like.