Change of VFS appointment

Does anyone have experience rescheduling their VFS appointment once it is confirmed? We have our appointment scheduled and confirmed in March in SF, but due to family issues and the timeline to be in Portugal (within 90 days after approval) for the AIMA appointment we will need to reschedule our VFS for sometime in May/June. Does anyone know if there is any risk in rescheduling other than maybe getting the VFS appointment later than we might like? Thank you in advance for any suggestions or information.