There's a ton of great ideas out there. Google it or check Etsy or even DIS boards. We have generic fun stuff for kids and useful stuff for cabin gifts. DON'T STRESS! This is not 50 amazing gift time! It's all for fun. I loaded up on fun stuff at dollar stores and put together bulk purchased items for cabin gifts.
One thing we did was make a postcard and magnet using photos around our property in Colorado (we have 36 acres)- no pictures of the livestock or family just plants and the view. It's part of the cabin gift and cost about $1 for that piece off of zazzle. I have fun disney stickers for kids (that's why I wanted to know favorite characters). It's not about going into debt- my son will be thrilled to find a sucker or a mickey mouse sticker.
Crayons, coloring books, charms, stickers, temporary tattoos, bubbles, snap lights, nothing expensive think fun. You're not providing souvenirs you're giving treats.
Hope that helps a bit.