This is kind of a silly argument. You guys know the convention is not the House of Representatives. It's about getting the party excited and mobilized. Eva Longoria (and Kerry Washington, Julia Louise-Dreyfus, Jennifer Hudson, and John Legend) fans tuned in and got excited, so mission accomplished.
But I definitely agree that we should avoid placing celebrities with no legal/political experience in actual positions of political power. Glad that's not an issue these days! (As an aside, man, I miss the Apprentice; what ever happened to that guy?)
If Eva Longoria's presence at the DNC is how you feel better about voting for a celebrity candidate whose decision-making has caused countless preventable deaths, I'd urge you to reconsider.