It's not the fact that you have 2 DC, it's the fact that the youngest is 7 weeks old! Little babies make the simplest trips difficult. I think you shouldn't expect so much from yourself. I don't know how old your oldest is, but if s/he is toddler or preschool age, that will makes things more complicated too.
As baby gets older, things will get easier. As for being late, I will tell you the best thing to do is give yourself an extra 30 minutes before you leave to makes sure your diaper bag is packed, baby is changed, bottles/sippies are ready, older sister/brother has gone potty and give yourself 15 minutes to struggle with them in the car. It just takes longer with more kids.
Our church in our last neighborhood was 10 minutes from our house. Mass started at 11am. After our twins were born, I'd start getting everyone's bums changed, shoes and coats on, babies strapped into infant seats, etc., at 10:10am. And we'd always walk through the church door with about 2 minutes to spare. You just have to plan more time in there to do EVERYTHING with little kids. It gets easier.
" I object to violence because when it appears to do good, the good is only temporary; the evil it does is permanent." Mahatma Gandhi
"This is the ultimate weakness of violence: It multiplies evil and violence in the universe. It doesn't solve any problems." Martin Luther King, Jr.