2 new additions!? Mazel tov!
If you can already brew 5-gallons AG, you can do smaller. But there are a few considerations. Scaling recipes is theoretically just using the right proportions, but I often use BeerSmith’s “scale recipe” feature for the first pass, then I go in to shift amounts to ‘sane’ quantities.
You can only buy whole packets/vials of yeast, but there’s less need for a starter.
Most 5-gallon recipe “kits” are designed to minimize wasted hops. That can go out the window when you scale-down the recipe. So if you have a 5-gallon recipe that calls for 1-ounce each of 3 different hops, and you cut that in half; you still have to buy 1-ounce each of 3 different hops. So unless you do some planning ahead, you’re still paying for an ounce and a half of hops that won’t be used in that 2.5 gal batch.
If you buy in bulk already, the cost seems to scale more proportional to batch size; what holds true for any non-kit brewer holds true here: minimize cost by bulk buying your most-often used ingredients. I buy Centennial and EKG hop pellets in bulk (for my go-to IPA and Irish Red recipes respectively) I have big sacks of 2-row and MO for the same reasons. I usually head to the LHBS for yeast, specialty grain and other hops. This makes me feel like the brew only cost me under $10, but obviously I’m not considering the base malt or bulk hops in that.
If you’re used to outdoor brewing on a turkey frier; I would suggest boiling a pot filled with your target batch size just to get a feel for how long it takes to come to a boil. If you can get the timing down, it would be perfect to have the boil start at the same time as the afternoon nap. Play with the kids during the mash, so they’re good and tired.