Sounds good to me, except the live stock. You can only have one male betta in a tank, or else they will fight, but you can keep more than one female in the same tank. Also, the betta fish will probably eat the shrimp. My betta love java moss, he's always swimming through it or resting on it. The undergravel filter might cause problems with the plants, so you might want to consider a small canister or hob.