It did not used to matter.Then it was the orange or yellow tomatoes that were low in acid. But recent years even red tomatoes have been bred specifically to be low acid. Certainly lemon juice will work as well as vinegar.
It totally depends on the tomatoes. As has been posted, the safest thing besides using them in cooking quickly- would be to start over- new flats. It does sound like you have your hands full. Good luck with the little one coming.
Looking through seed catalogues, I have come across varieties that are mentioned as being "old fashioned" canning types, higher in acid: varieties such as Old Brooks and Bonnie Best.
Who would even want to eat a low acid tomato?
Makes zero sense.