Help with proper waste/vent fittings

Howdy, a quick question: I'm putting in a 3" ABS waste/vent stack to replace my existing 4" CI one. This stack serves two bathrooms and a washing machine. Because of the back-to-back layout of the bathrooms it will have vent and waste inlets on both sides of the stack. I know for the back-to-back toilets I need a combination wye-tee, but then I have two 2" vents coming in above that point and two 1.5" drains below. For the vent I assume I can use a sanitary tee, but for the drain, do I need to use a double combination wye-tee as well? If so, can you just build them out of a wye with long sweep elbows (or something like that)? I ask only because I can't seem to find 3"x3"x1.5"x1.5" double combination wye-tees anywhere, so I assume either you can use a sanitary tee (doesn't seem right...) or a wye (seems logical)...though now that I think about it, you pretty much have to build a combo wye-tee in order to connect to the wye...am I making sense?

How about a 3" double fixture fitting and a couple flush bush fittings to reduce it.

Sounds good to me..thanks!