I don't know what your family's needs are specifically, but there are several fantastic Augmentative and Alternative Communication (AAC) tools out there that are open source and in active development. The community is very friendly and they always welcome help from experienced software engineers. I personally contribute to Cboard (https://www.cboard.io) and a few others but check out the OpenAAC website (https://www.openaac.org) for additional resources :-)