Sorry, I just realized West Virginia (if that's what the WV in your handle means) uses the IPC. Under the IPC, you're going to have to match the size of the dry vent to largest portion of the wet vent, i.e., 3". Your inspector might let you get away with 2", but you might also have to convince him that your laundry tub constitutes part of your "bathroom group," since it's in another room. On a different note, why don't you try to dry vent all the way?
Yes, I am in WV so it's IPC. I haven't tried dry venting all the way because the shower trap connects to the drain under the wall and concrete behind the shower and Already right over top the horizontal line to te main soil stack. Which reminds me, I could swear I saw something about vent or drain requirement if you are within a distance of the soil stack but can't seem to find it now.
Right now I have the shower drain attached via sanitary tee and that us all, but I put a 2 foot pipe in the top and put a hose in it to simulate draining with no effective vent and it didn't seem to siphon, also pour water from a bucket and drained fine. If it seems to work I may just have to take my chances. I live outside city limits so no local inspection. If I have siphon problems I can maybe raise the shower later to add a direct vent, but don't want to give up the head room if I don't need to.