Welcome!
What is your current savings rate per month? I ask because I'm about to recommend you take your $15k E Fund and send it straight to your student loans, then put the rest of it into Roth IRAs for both of you. The reason is, if you are saving $$ each month and you face an emergency, you will be able to pull the cash from your monthly savings. Many "emergencies" don't need to be paid for 30 days (if you put it on a cc), and in those 30 days you have a lot of options -- save for it, take out a HELOC, take it out of your Roth (as long as it's just the principal, there are no penalties), find a side hustle to cover the expense.
(As for where to start the IRA, I recommend Vanguard, with an index fund, and many MMMs recommend the same thing but it's up to you. I like Vanguard index funds b/c of the low costs.)
As for not having a monthly habit, I recommend simply setting up a savings transfer on a timeline that works with your income -- once a month, twice a month, etc. If you don't already have an idea of where all of your money is going, write it all down and tie it to the dates when you make those payments, and you will find a good spot for your regular retirement contributions. Now that your Roth IRAs are all set up, those transfers will be easy. Just set it and forget it.
The passive income through land lording is great to have on the horizon!
The other thing that you have on the horizon is your return to the workforce when your kids are school-aged. Is there anything you can do now to prepare for that -- gaining skills, volunteering, meeting people and networking, etc.?