Turning up and putting them off is one way to go.
However, you can potentially save yourself even that trip.
Phone up the court and explain you've already got plans for those dates and ask if they can fit you in SOONER. Most people try to put if back, which is when they'll ask for proof of whatever it is you're planning on using as an excuse.
If you ask to serve SOONER they will try to accommodate you without asking for proof of unavailability for initially scheduled dates.
The thing is, as they need to fill these slots up quickly, they'll register your intent and you'll go on the reserve list for an earlier trial which have already pretty much got its set of jurors allocated. Subsequently, there is a very low probability you will be called at all. Worst case is you are, and then it’s plan B – mega-stupid or mega-opinionated racist, sexist, whatever-ist….
Having been on the reserve and not been called means you will not go back into the system until after whatever mandatory cycle exists in your state makes you eligible again.