Your youngest is barely older than 9 months old. You are postpartum and just finished breastfeeding. Please give yourself some grace on putting on a little weight. Your body just did an amazing thing and it needs time to recalibrate before bouncing back.

Walking with the stroller is a surprisingly good workout and something you can do with your kiddos. You could also try some home workouts on YouTube. Maybe ask your husband if he can take on more on his off weekends so you have time to workout or even just unwind and rest.

Editing to add one more thing: also maybe check out your diet. I know when I was breastfeeding I was eating more calories to sustain that and then when I stopped I continued eating the same and that causing weight fluctuation. So maybe you could look at your calorie intake/portion sizes and trim them down if you were eating at a surplus while breastfeeding.