I have never had the opportunity to go to an Easter Vigil myself and I have a couple of questions also:
What if you are physically unable to follow in the procession? Would it be inaapropriate to sit in the pew?..
The Roman Missal describes different ways the Easter Vigil can begin.
“7. All the lights in the church are put out.
A large fire is prepared in a suitable place outside the church. When the people have assembled, the priest goes there with the ministers, one of whom carries the Easter candle.
If it is not possible to light the fire outside the church, the rite is carried out as in no. 13 below.”
For this to work well there needs to be a large bonfire, perhaps seats, perhaps shelter in case of rain.
The Roman Missal has this other option:
“13. Where is may be difficult to have a large fire, the blessing of the fire is adapted to the circumstances. When the people have assembled in the church as on other occasions, the priest goes with the ministers (carrying the Easter candle) to the church door. If possible, the people turn to face the priest.
The greeting and brief instruction take place as above in no. 8. …”.
So at one church you may find locked church doors, but hopefully some thought given about how people with disablilities can enter and be seated as part of the procession. In another church it may be a case people assembling as normal in the church.