If you're from a fam that's already full of kids, there's no way to avoid a bigger party. It will be joyous and noisy and messy. The best option for managing more guests is to outsource where possible. A fun theme that can be done in your backyard or the local park is a Teddy Bear's Picnic party. Friends can BYO a rug and picnic baskets of snacks if you want to keep the vibe casual and not blow out on budget, or you can get your Pinterest game on and cater with lots of nostalgic checked blankets and platters of yumminess. I highly recommend either an entertainer if there are a lot of children as it takes the pressure off the grown-ups, or hire self-managed entertainment like soft play pieces, a ball pit or push cars.
Don't forget sticky name tags for any bears the kids might bring along. The last thing you want to be handling is a treasured friend going missing. A name and a phone number will ensure they'll be safe throughout the length of the party.