How Do I Explain This to My Toddler?

My baby has cCMV, a common viral infection I contracted while pregnant that attacked his brain before he was born. (If you are pregnant, ask your OB or Midwife about the TORCH test. Visit StopCMV.org for more info.) Because of how the virus affected his brain, he has developmental delays and is at high risk for hearing loss, vision loss, and seizure. He doesn't roll, crawl, or sit independently, yet. He doesn't eat solids either. He may not for months to come. As he gets older and bigger, his delays will likely become more obvious. Although we hope he won't, he may eventually need assistive devices (wheelchair, feeding tube, hearing aid, etc.) and even if he doesn't, he may never be able, or allowed, to do everything his big brother can.
How do I explain this to my toddler?

Besides his pediatrician, he has a team of specialists and therapists, some who come to our house every week, others we have to drive over an hour each way to see once a month. Many days, I need to spend some time calling doctors, scheduling therapy sessions, reading test results, or researching possible symptoms and treatment options. There are times when I need to focus on the baby so I can make sure he does his exercises, or so I can try to catch a new symptom on video. This often has to happen while my toddler is awake and wants my attention. Sometimes it means that we have to miss a play date or skip an outing or activity.
How do I explain this to my toddler?

There are some days that all the stress and uncertainty get to me. I just don't want to deal with any of it or the usual "Mom Stuff" and any little thing may set me off on a crying jag or a furious tirade. Those little things are usually the typical toddler stuff that aggravate most moms. Sure, I'll feel bad about it later and have to apologize to him, but right now, yelling, or hiding in the bathroom with a beverage and my phone are the only way I can keep my tenuous grip on any semblance of sanity.
How do I explain this to my toddler?

I explain it all to my toddler the same way I explain most things: honestly, simply, and with empathy for what he's thinking and how he's feeling.
The reality is, we love him and we love his brother. He and his brother love each other. We pull together as a family and support each other. We have amazing friends who care about us and find ways to show us they care. That is what matters. It is what will help us through whatever comes our way.
To our wonderful friends and family:
Thank you! Please don't think we don't want to spend time with you. Sometimes it just is too hard. Keep inviting us and including us. We appreciate that you care and want to help, even if we decline time after time. Keep offering, we may NEED to accept your help at some point.