Your idea of a donation honoring her son seems lovely...I think most people would be appreciative, but I agree with you on checking with her first.  Grief can be so personal that some people don't want it publicized.

There's a private web community called Hannah's Prayer Ministries...it's a faith-based group and is for women coping with infertility and loss of children.  (On the www it's hannah.org you you can google Hannah's Prayer).  If she is person of faith (from what i've seen it's fairly conservative Christian), she may find it helpful.  I agree with Meri that professional counseling may also be appropriate (in time).  A lot of private counseling centers have someone who specializes in women's issues and may be able to link her with support groups as well.