I would look at ways you can up your income both now and when the baby arrives. This may be more on your husband since you'll be a bit out of action for a few months, but realistically does he currently work 7 days a week? Could he diversify for example offering hedge trimming, garden clearance, even rubbish removals on a weekend if he has a van or truck. If he could do even half a day extra on a weekend that could easily be an extra £50 to £100 a week, but the important thing is to look at ways to diversify rather than looking at the business as 'this is what we do' because he can't ask his business partner to work 7 days a week.
Outside of his current job could he take on a second one? My husband did takeaway delivery for a year or so when things were tight. Again, made over £100 for 2 nights a week work, and really helped us out when the kids were small.
What can be done from home? I'm not talking about doing surveys for 20p a pop, but sell any of your unusual or designer clothes and shoes that don't fit, kitchenware you don't use, kids games that haven't been played with much on facebook or ebay. Matched betting, we've done all the opening offers once for both me and my husband, made £2-£2.5k each - this is NOT gambling and should not be done by anyone prone to gambling, but if you can use a spreadsheet it's pretty simple, there are guides on the Moneysaving expert Up Your Income forum. I have a couple of non facing youtube channels, so relaxation music, tutorials etc. I also have print on demand stores going, I have a couple of thinkific and skillshare courses, those same courses I have in a mini format in several kindle books, and I'm just exploring a FBA business on Amazon. You can knock out a kindle book in a couple of evenings once you break out of the mould of thinking it needs to be a 300 page work of fiction, what do you know that not everyone does? Can you write 30 pages on flower arranging, intro to stained glass, how to navigate the building regs system, 10 mistakes to avoid when buying your first home, 20 recipes in a waffle iron?! I also have a print on demand store with Merch by Amazon, Etsy/Printful and Redbubble. Almost all of it is simple, text based designs using Canva, no need to be a great designer and once I hit 200 designs or so I was getting at least one sale every day, so it's not huge money while you build a portfolio, but it requires absolutely no ongoing effort so it's good to tick away in the background. I wouldn't recommend doing them all at once but pick something that appeals and hit youtube, find a tutorial for how to do it (and there are LOADS) and start to diversify your income. Hope that helps x