Most people in the general population seem to believe that the size of the breaker indicates the size of the load, but that's nor true. Breakers (overcurrent protection) are installed to protect the circuit. We don't know the actual load of your RV. We only know that one of the standard feeders for an RV is 50A, but if yo are just parking it and the only thing running in it is the refrigerator and the water heater. Then what's the load? Or are you using it to park an RV for someone to live in/ Then what's the load? Are you going to be using the hot tub and the RV at the same time? Once again what's the load? It appears you are using this panel to handle a current feeder of 100A. What's its current load?
So you can see that we really can't answer the basic question of whether or not the service to the panel can actually operate since we need addition information about your entire dwelling. Can you add 2 - 50A/2P breakers into the existing panel? It looks like you can, but the photos don't even show if you have a ground and it doesn't show that you have a neutral. Are you going to have any 120V load? Also it shows your line in was attached to your bus by drilling two holes in the side of the panel. This is a very dangerous situation since the current carrying conductors are not bundled and this is causing mutual induction in the panel itself. This can cause electrical shock and potential melting of the insulation of the conductors.
In short you are wise to get an electrical contractor on your project as soon as possible and let him work the through the details before you start your projects