Katherine,
I think anyone who is an advocate of breastfeeding faces these dilemmas. I
believe in taking the bull by the horns and not waiting for the topic to come
up. If I were you, I might consider writing him a note of condolence on the
passing of his wife, and then expressing your concern that he might possibly
feel uncomfortable with you and that you don't want him to feel that because
you support him 100%. If you've already expressed condolences, then make it a
personal note welcoming him back and letting him know the same. Something to
the effect of, "I am looking forward to seeing you again! I know that our
original relationship was based on breastfeeding advocacy and studies, and I
am concerned that you might possibly feel awkward--- please know that I
support you in your fathering 100% and that my concern for you is for your
relationships, and not feeding methods. I am so thankful for you that you
have your daughter, and look forward to seeing you both."

Anyway, you get the gist. I'm thinking that writing a note will lay the
groundwork so that your first in-person meeting can happen without the
baggage of worry on that issue. I also think that these things can be worded
best in writing rather than in person and on the spot.  Please let us know
how this turns out; I grieve for him also to have such a devastating thing
happen to his family.

-Lisa Marasco