New kittens meet adult cat good new or bad?

so theyre all in the garage bc theyre outside cats. now at first the adult cat izzy was just hiding and hissing but now she's coming out and still hissing some but she let me pet her and one of the kittens at the same time. im trying to make sure she knows this is a rewarding experience by spending more time with her but also the kittens. so is this progress or is she just saying she's boss and it's trouble? also when should i open the garage? im scared that the kittens will run away right now since they just got here. im also scared they'll venture too far and get on the main road where i lost izzys sister. plz help izzy, midnight, and patches!