I think you would need size large for James, or xl with growing room. You can also get sample size pots of lanolin to try from some places. I have 2 soakers for night and I usually wash every few weeks but that all depends on how whiffy they become.
I leave them on a radiator airer to air or pop outside on a nice day. We use dedicated night nappies though or Emmet would not last the night. You would have to boost them well IMO.