I think you have plenty to start with!
playdough,watercolors and washable markers are the most used craft items in our house (I have a 5 and 3.5yo and they do art projects daily).
We have lots of pom poms,glitter, feathers, buttons, pipe cleaners, shells, buttons, sequins, sand,etc. too but they don't get much out of that currently creatively anyway, it's more a sensory process.
Lately my 5yo is obsessed with making stuff out of recycling and painting rocks and pieces...