Go for it Teak ..................
If anybody needs persuading, then let them try to skim a ceiling without PVA. The old plaster will suck the water out of the skim before you can get it off the trowel. PVA reduces the suction so that the skim "dries" by chemical reaction alone ..........
It also regularises any differing backgrounds you might have ........ for instance, bare plasterboard, old skim, old lath & plaster .......... so that they all react the same.
Somewhere around 5 to 1 water to PVA. No need to let it dry out completely, but it must be tacky enough so that you don't bring it all off again with the skim. Everyone has their own preferred system, but you shouldn't go wrong with this method.
Sel-adhesive scrim cloth on the cracks............. no need to fill them. Put the scrim on just before you skim, so that the plaster can get into the cloth and the plaster is then "re-inforced" a bit like GRP fibreglass....... if you know what I mean.
How big is the area, and how high is the ceiling?