Singing lessons at 3. Oh my goodness. ( I have taught group singing to 4 year olds and that is the absolute youngest it should be, individual lessons not til age 10.
At 3 one or at the most 2 activities should be plenty. At 2 dd did rhythm time a toddler music group. At 4 she did ballet & Stagecoach. That was ample.
I do sometimes see these burnt out children in our classes, I'm a big fan of some organised activities but it has to be in moderation and geared to what the child's own interests are.