Raising soil level around conifer trees

Hello  My garden is on a downwards slope, and at the bottom of the first grassy slope is a row of conifers then a  broken retaining flint wall. There is a dip between the end of lawn and conifers. We would like to level the grass area as much as possible & replace the existing retaining wall. However, to do this we need to raise the soil level around the conifer trees by a foot or two. Does anyone know the impact of this on conifers? Other options would be make retaining wall in front of trees (not ideal) or remove conifers. I'm not opposed to this however it's a fairly big job and currently offers us privacy from the houses behind which overlook our garden.
Many thanks

I thought that might be the case, thanks. I'll have to have a think about it