If you do not want to waive time, you can keep the May 7th trial date. If you want to reschedule, then it appears you will have to waive time. It's your call.
If you reschedule and for some reason the officer does not show, the matter might be continued or it might be dismissed. You can always make a request that it be dismissed, but there is no guarantee - especially if the officer had a good excuse (vacation, illness, training, a priority call while enroute, etc.)
So, if you want to extend the date out, waive time. If you want it within that 45 day window, accept the time you have on May 7th.

