Oh how fun. So below the prices kind of range and you can pick what is comfortable for you:
* Clothes-- Super easy and fun. Think Disney t-shirts, PJs, swimwear, socks, heck even underwear! Tons of options.
* Accessories -- hats, sunglasses, footwear (flip flops, slippers, crocs, etc.), hair clips and bands, jewelry, purse or bag
* Practical stuff -- bandaids, sunscreen, santizer, masks, backpacks, etc.
* Entertainment -- books, DVDs (if that's applicable - many just stream), coloring books & crayons, stickers, autograph book with pen (I did a pillow case for my kids with fabric markers and they still use them)
* A homemade GC for an experience or treat -- think something like dining at Cinderella's Castle or Pirate's League (mermaid makeover or pirate empress, anyone?), a Disney ice cream, etc.
* Toys -- plush, dolls, figurines, games, etc.
* Snacks -- fruit snacks or the mickey goldfish, etc.
* Kitchenware -- fun water bottle, refillable mug, etc.