Mr. Bo is adorable, Tui! As for recommendations for your kid, I have a couple books they may like. Then again, it depends how developed they are in reading. The first one would be Spirit Animals (I know you’ve heard of them, since you wrote my favorite book in the series xD). Lockwood & Co. is good, but maybe too advanced for a third grader. Michael Vey is amazing. Not sure what grade it’s for. If you’re doing read alouds, it shouldn’t be bad. Mister Max by Cynthia Voigt is pretty good. Fablehaven by Brandon Mull is AMAZING. If your third grader is a girl, she may like Pegasus by Kate O’Hearn. I hope some of these may interest you two :D!
P.S. Holes was an amazing book. I’ve read it three times already xD