Hey there,
Okay, you've got a bit of a complicated scenario, and I'm an American so I don't know if my advice is kosher.
You should be able to terminate one of those contracts while maintaining the other as long as the contract is an at-will termination contract. Generally that means either party is welcome to terminate employment at any time with no predefined length of employment. Employers aren't supposed to terminate the other contract out of spite.
Reality: It happens. There are certain circumstances that would justify them terminating the other employment contract. If one job you hold is dependent on the contributions that you give with your other job then they have justification.
If you work for a small business it's well within the bounds of reality that a pissy employer may choose to terminate both. There aren't that many circumstances that would grant you recourse either unless they flagrantly violated an equal opporunity act or some such.
My advice: Talk it over with your employer. If you approach them in a mature and diplomatic manner and explain why you're looking to make this decision they'll look on it more favorably. Usually. You may want to pose it as an option that you might pursue, and would like their input or recommendations. If you work with them most employers are more reasonable that we give them credit for. This is not legal advice! I'm not a business lawyer so I don't know everything about the subject. Also, if things go wrong I live nowhere near you and go by the alias Tercha. *Points at Tercha*
