This gives them stuff to think up which you might not have thought of. Selling points you might have missed. They can't be against ideas they came up with. It gets them involved and lets them think they are part of making the decision instead of being sold. Strategy is the key here.
Women love thinking about grandchildren.
Give it some time and don't let her think you are pressuring her. Let her relax and reel her in slowly. In the end she'll jump on board, and you won't even need to use the net. You might need it about as often. And the rest of the time it is an accident waiting to happen.