Kittens born outside!!

We have had a stray cat hanging around our house for a couple weeks and we noticed she is pregnant so we decided to feed her and give her love outside. We have 2 cats inside and had twins on the way so bringing her in wasn’t an option. I just had my twins via c section 5 days ago and they are in the NICU. We come home from visiting them today and SHE HAD HER KITTENS in a tub outside that was laying on its side. She isn’t laying with them and is just walking around us. Should we tip the tub over and put a blanket in it and hope she will climb in it and feed them? We are still providing her food and water but we absolutely cannot bring her inside. What should we do with these cute little babies?!