Good luck Mommy!
I am in a similar boat - I've only been riding 2 years and I am doing my first mt bike race in August. My kids (10,11) seem uninterested, but I think they are worried, just don't want to say. My 19 yo comes right out and says she is worried but she is very supportive. My parents - can't even tell them!!! they would have me committed.

I'm 46, and I'm racing as a pair with my partner - he has done this race solo before. I was his support person for 4 races. One of his team mates had a 5 year old, and she went to the race. She cried and hung on to him each time he went out for his laps.
So it could be concern (with your kids) or they see you doing something that is not part of your Mommy role and that makes them uneasy. Or they see your riding as competition because it takes you away from them. I think my kids have felt all these things.

Eventually, it will become a normal part of life the longer you ride. I've been riding almost daily since Feb to get ready and I've seen things change over time.

And you are being a good role model!!