We wouldn’t say that a family is ‘relaxing’. We might say that ‘being with my family is relaxing’

It’s ok, but it sounds more natural to say ‘my family is warm and relaxed’.

You can say it, but it sounds odd. If you want to use the adjective "relaxing", then you should be more specific about what exactly relaxes you. Is it the atmosphere? Is it their good nature? Is it the fact that they treat you well? One approach, the one taken by David, is to say that it is their presence that makes you feel relaxed: "Being with them is relaxing". Other approaches: "My family's home atmosphere is warm and relaxing." "Conversation with my family is warm and relaxing." "The friendliness of my family is warm and relaxing." You cannot fix the sentence by replacing "relaxing" with "relaxed". The sentence you get would be grammatical but its meaning would be different. "Relaxed" is how they feel, but "relaxing" describes how you feel.

Yes