A warm sound will be achieved by the tuning of the head. The tuning will also help with a focused sound as well. The beads of the stick are going to be the biggest concern to get the most focus. I prefer a barrel/ball style bead. My go to stick for kids is the Innovative Percussion IP-LD. This will give a "longer/wider" tone.

You can also use an acorn/teardrop shopped bead which will be a more "focused" sound. The sticks I like here are the Innovative Percussion IP-JC, IP-CL1, or the Cooperman Mike Rosen.

A lot of the sound starts with the tuning of the top and bottom head.