Single or double stroller?

We are debating what to get.. single or double.

Our daughter will be 2 1/2 when our son is born. We won’t be using the stroller too much because hubby travels for work but will be using it sometimes to go to the zoo, shopping, maybe a few walks. Definitely not everyday though.

Should we get a double considering we will still have a 2-3 year old? Or do kids at that age typically not sit in one? Also, we were at buy buy baby looking at some and they all have a max weight of like 45 pounds. Our two year old is already about 30 pounds, maybe a little more. (She’s tall) so we are confused. Thanks!