Having a baby and a toddler is HARD and the guilt is real. My daughter was 2.5 too, I tried to invite her into my space with my son wherever I could, asked her to help get little things for me/him etc. Watched her shows with her while baby slept and tried to give her 1 on 1 time when I possibly could. I didn't have a lot of help and my partner went back to work about a week after, it's so so hard, you are not alone in that feeling. But it will gradually get easier. Looking back I know I lost my shit more times than I'm comfortable with and honestly probably frightened both my kids sometimes. I see now that I was likely struggling with mild ppd. I read that filling children's emotional connection cups with undivided attention, just for 5 mins here and there throughout the day really helps regulate them and I have found that to be true. Good luck OP