hi there mamma!
I think you could do some awesome indoor activities that will enrich their lives as much as going out, and besides is not like you are planning on keeping them inside all the time just while the weather is too cold to go out, you could also try and find places where you could take them that is "out of the house" but not in the outside like malls or indoor parks this way they get to get out of the house but you wont have to deal with the cold.
Remember as much as their needs are important yours are too and if going out will make you stress out too much that will affect your mental health you should just don't do it, also make the dad or another care giver who you could ask for help take this tasks into their hands.