fish for my 10 gallon

IMO red eye tetras and zebra danios are not good choices for a 10. The red eyes can get quite large, and zebra danios would appreciate more room (mainly length) because they are so active. Sometimes a male betta and males guppies can work, but often it won't because make bettas will go after the guppies because of their big tails.

It's true they can live in there, but I wouldn't do it. The red eye tetras can get almost 3 inches long and like to be in a group as I am sure you already know. The zebra danios also like to be in a group. The general thought on a "school" is that it should have a minimum of six. If you had 6 red eye tetras, 6 zebra danios, and the bottom dwellers that you want, plus some shrimp and a snail it is going to get over crowded fast.

Sounds like you already need a bigger tank for all the fish you want!! I would not add a betta and guppies to your already pretty full tank. Bottom dwellers are a good idea, how about some shrimp?

Corys are the best bottom cleaners in my experience....and....they're CUTE !

Maybe 3 smaller sized cories for the bottom.....folks always say cories need to be in larger groups than that, but as long as there is more than one, they can do fine. A single cory all by itself will stress out and not last very long.
If you decide on a couple of those, make sure you choose the smaller variety. If you pick pygmy cories (if you can FIND any)..then you could probably go up to 5 of those for your tank.