Pommy said it much more nicely and more maturely than I did... and I agree with her 100%. Him going on this vacation is cake-eating. Don't facilitate it. It isn't fair to you (or him, honestly, if he doesn't get to see what S and D is really like.)
Me (46) H (42) M:14 T:18, D9 & D11 4/19 - 12/19: series of escalating BDs 9/20 - present: R and piecing