Can I use 1 iPhone to receive FaceTime Video calls from 2 apple IDs? Mine and My Children?

Long story short, my ex won't allow our children to call me on my personal phone when they are with him. I am expected to carry their iPad with me everywhere I go in case they call me. I refuse to pay for a data package for an 8-year-old iPad and refuse to carry this everywhere I go.

I'd like to add their apple ID to my phone only for facetime calls but also be able to take facetime calls on my personal apple ID all on my personal device and negate this iPad all together.