Advice for 5 year old who seems sad?

I have a 5 year old daughter, and a 3 year old son. My daughter loves to play pretend and talk (a lot!), but my son is autistic and nonverbal so they barely play together. She relies heavily on me for play when we are home, which is often now that it is summer! We are also in TX and it is unbelievably hot so we are not outside as often.

We have a play date with our next door neighbors who have a 6 year old daughter several times a week, but we don’t see her friends from school very often because everyone seems to have conflicting schedules! So we end up meeting with a friend from school a couple times a month.

My daughter seems really upset about it. When I’m not playing with her (because we all know as moms we can’t play 24/7) she ends up laying in her bed or moping around in front of the tv. I offer her activities to do on her own but she refuses. She just seems really down whenever someone isn’t occupying her.

On one hand I think she needs to learn to be satisfied playing alone and use her imagination. On the other hand I have a lot of mom guilt that I’m not able to socialize her even more, and feel sad that seems so sad.

How often do your little ones have play dates through the summer? What do you do to keep them happy and busy in the summer (when it’s 100 degrees outside).

Keep in mind we have a really hard time going places with my son. He elopes and has intense meltdowns. So for example, I can’t do a public pool alone with both kids during the day while my husband works.