fingerspelling != sign language

In sign languages facial expressions and body language function as core grammatical tools known as non-manual markers, used in grammar and syntax, distinguishing adverbs and adjectives, indicating tone and intensity. Classifiers, abbreviated as CL, are signed morphemes (particularly, classifier handshapes) that represent a group of nouns or referents. Fingerspelling hand shapes are the building blocks for the hand-related elements of the language (signs done with the hands) whose meaning is dependent on the context, much like a spoken language's word's meaning can be affected by where in a sentence it is placed, tone/pitch, etc.

From a technical viewpoint, if you intend to push beyond where most projects similar to this one have ended up, it might be interesting to consider SL handshapes as analogous to tokens in an LLM, vector encoding them to capture the context and semantic meaning.

From the human relationship POV, making an effort to learn full natural sign language to communicate with your relatives will no doubt make them very happy and enrich their lives and yours.