Yeah, Betta's won't swallow rocks or sand, that's a misconception. They will pick them up but they can't swallow them or won't and will spit them back out, even with sand which is smaller than their pellets. I have tanks with sand, some with gravel, other's with dirt and some that are bare bottom and have never had issues.
As for toy's there a bunch of things you can do. You can use ping pong balls (wash them off first) and he can play with them. You can use the floating mirrors you'd buy at a petstore but don't leave it in all the time. He can exercise for no more than 15 minutes daily with that. You can also use Craft Mesh from a craft store and make a Betta Hammock out of it. Basically take a strip and sew it into a cylinder (make sure to cut off any sharp pieces!) and he'll rest in it because it floats!
There's a bunch of fish "toy's" you can make, ask around on the forum and people will give you ideas sometimes ^_^ also look at DIY threads (Do it yourself) and those will have some great ideas as well!