If you’re looking for alternatives to Harry Potter for your kid to read, try “So You Want to Be a Wizard”, an 11-book series by Diane Duane! She is LGBT friendly, and openly has LGBT characters in some of her other works!
If you’re looking for other books for your kids with magic, I also recommend “Percy Jackson” by Rick Riordan! He has many openly LGBT characters in these books, and is very supportive of the community :)) These books also age very well, and are a good read even as an adult!