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Look at using EI for SFO/ORD/BOS-DUB, and AA/US for PHX-SFO/ORD/BOS. You'll have to call BAEC to check award-seat availability on EI. Note: BAEC may try to charge you the higher "multi-partner" redemption rate if you try to combine EI with either AA or US on a single redemption. If so, you will have to book the different airlines as separate redemptions. And if you do that, leave extra time (maybe even an overnight) for your connections, as you will not be assured any protection in the event of IRROPS.
The cheapest roundtrip Coach redemption will be PHX-BOS-DUB-BOS-PHX for 50,000 Avios per person. Going via SFO or ORD will cost 59,000-60,000 Avios per person, roundtrip.
Note that EI also flies BOS-SNN, in case flying in (or out) of SNN is an option for you.
You do not want to use your Avios for TATL travel on AA or US, as doing so will incur hefty surcharges. The surcharges for TATL award travel on EI are quite modest.