I would think that the lava rock would be harder to clean than regular gravel, because it will have more of a pourous surface and an irregular shape for waste to get cought in. I would stick with the normal stuff.
As for your plants....remove any damaged or dead leaves or stems. Remove any rubber bands, lead weights or from pots. Rinse in clean water and look really close for any snail eggs or other forign matter on the stems or at the base of the plants and remove. Find the perfect spot in the tank and enjoy.