In the sketch below, is it acceptable to have the shower and toilet wet vented by the lav. like that (as long as my distances from trap to vent are within code)? Thanks!
Not a pro.
Yes.
A two inch properly used vent can do it.
A shower wet vent starts within five feet of the shower trap if memory is correct.
It has to come off the top off the shower drain line. A wye rolled up 45 degrees or more. Toilet enters main line after shower.
You can wet vent a bathroom group with a two inch vent.