What would you do??

My husband and I are healthy 26 year olds.. we’ve been trying for our first baby for almost 4 years. We did IVF and have 6 day 3 embryos that are frozen. We transferred 1 of our embryos on 10/19 and it failed... We are devastated. We are thinking about getting an ERA (endometrial receptivity array) done which could tell us if we transferred too soon or too late. It will basically tell us when the best time to transfer is. This will cost anywhere from $800-$1400. My sister in law has offered to be our gestational surrogate out of the kindness of her heart if we would like. She has had 2 really easy pregnancies, which resulted in my healthy nephews. I on the other hand, have NEVER ONCE been pregnant. My question is.... should I do the ERA and transfer to myself once more with 2 embryos or should I just let her try to carry them??