35mm film is the easiest to develop without concerns of light leaks or uneven development. Using the developing tanks for 35mm can also save on chemistry (note: this process is the same for 120mm film, minor changes in the loading of the film and chemistry amounts).
The photographic chemicals used in the lab should not cause any problems if they are handled carefully. If you experience any sensitivity to the chemicals take extra precautions to reduce exposure. If you are pregnant, or become pregnant while you plan to work with photographic chemistry, stop and seek a professional opinion for your safety.