On 1 Gen I would declare a PAN for sure... You won't call out the Emergency Vehicles, they will be on Standby though, and if you would lose your last Gen, you need them within 30 min, which is a MAX time...
One Hydraulic (Standby counts as one) and one Engine would be a Mayday...
Distress calls are not an exact science though, so we could discuss this forever..