EACH trap needs its own individual vent. A tub drain might be as small as 1.5". A washing machine drain needs to be at least 2". So, probably not, but it would depend on how things are layed out. If each trap is properly vented, then, no, neither should siphon the other. Some places do not allow an AAV, so even if it might work, it would not be to code. It is always better to do an atmospheric vent if possible. Keep in mind that an AAV can only let air in, and depending on where it is, sometimes air needs to come out as well.