Kids away for summer vacation

I let my children stay with my father for the summer since we moved to another state. They were very excited to go and I agreed to let them stay until I have my baby in July. At first I was ok but the minute I knew it was time for me to leave them I cried and I’ve been crying for 3 days now. I don’t know if it’s hormones or if I really just miss my babies. They have NEVER been away from me for more than a few hours. It is always me and them at home and now I’m here alone. I don’t know what to do to keep my mind off of them being gone and enjoying themselves. Any suggestions?