@christygb You have some very exciting and positive things ahead of you!
A few replies have already touched on what I would say.
Fill out the donor questionnaire now even though it's early. A nurse will call you and go over your answers so that you'll have some info to start with.
A higher BMI may not be a "deal breaker". If you pass the initial evaluation, there will be many tests to check your overall health which will determine if it's safe for you to donate.
I thought I read in another post that Mayo doesn't do both liver and kidney transplants from the same living donor but can't find it. The nurse/social workers at Mayo are excellent and will be able to answer that for you.
Whatever the outcome of your evaluation is, you are doing great things. Deciding to lose weight for your health will pay off for you and your family. Inquiring about live organ donation means 1 more person in the world has info that they can pass on to others.
Good luck to both of you