Unless an engineer says otherwise,ALLWAYS reinforce framing members if they must be cut/drilled. In realality,a few joists in the floor wouldn't matter but there are others that would because they are bareing more weight. Framing is rarly overbuilt so it's good pratice to compinsate for altered framing unless one is experienced in the trade. Sistering 2' feet of 2x or 3/4tr plywood glued and nailed should be suficent.

Basic rule for drilling joist.

Do not bore holes closer than 2" from joist edges, nor make them larger than 1/3 the depth of the joist.

I also took a closer look at the venting requirement. The vent line to the roof is a 2" dry vent, so it looks like I can use 1.5" PVC to connect in my other vents from the commode, shower and sink, which will then require a smaller hole in the joists. I may even be able to route 1.5" PVC vents across within the walls, since they are not load bearing.

Bruce