My DD is autistic but does pretty well (likes school, has friends, is generally pretty happy in herself, etc) - she is 6. I do think it's a balancing act between giving plenty of down time but also giving opportunities to socialise. On social skills I think butting in too much can be damaging (maybe a little steer - but you want them to be able to manage without you).
There are a few books that DD quite enjoys. Firstly books about feelings (to help spur conversations about why people might behave in the ways they do, which can sometimes be boggling). For example, there are a few books by Molly Potter about feelings and friendships that are good (maybe a bit young but probably OK at 5). I think encouraging self-care is also important: teaching them to recognise in themselves that they are a bit different, and to learn when they need down time or if things are too crazy and they need a break. DD has a couple of books specifically on autism (like "All my stripes" by Shaina Rudolph & Danielle Royer and "Inside Aspergers Looking Out" by Kathy Hoppman). She doesn't talk about being autistic that often, but she does know that her brain works differently and she is more sensitive to some things, like loud noises, and does sometimes pick those books up.
DD has also started to enjoy a book called "Diary of a Social Detective" by Jeffrey Jessum, which we read together. It is about an autistic boy who helps other children in his class with social problems by analysing them. It's maybe a bit old for our kids but DD seems to enjoy it and likes the idea of being a detective.
Other than that, I think just encouraging their interests is important. In the long run I think they will find friends who are interested in the same things they are, so just encouraging those interests (and new ones as they crop up) should help them have plenty to talk about with new friends.
DD does do ballet which can be a bit of a challenge (particularly when we had to change classes recently as the old one was not really practical logistically with Covid and not wanting to get on public transport) - but she really enjoys it. I do feel it is somewhat good practice for being in different social environments too - though if I thought she was getting too tired or overwhelmed I would not push it - I see it as a "nice to have" but am always aware it may become "too much" at some point. She enjoys the actual dancing though, so she is motivated to do it for now.
Finally, I watch a lot of YouTube videos by autistic adults. Particularly Purple Ella, who is autistic herself but also a parent to three children, two of whom are also autistic, so she has some really good videos both on parenting but also the Autistic Experience.
www.youtube.com/user/purplemumify
Because you have it in your family, I suspect you are doing most of the things you need to be doing already. I now see a lot of autistic traits in myself, and I think it gives me a natural understanding of some of the things DD finds hard because I found them hard myself but got through it or found ways to do things that worked for me.