Sports day / Relay race
Speaking of regressing to your childhood. Why not have a sports day/ relay race in the garden? I highly recommend that you do a test run of whatever games you are including so that you get an idea of how tricky they actually are. My super fit sister set up the space hopper section of the relay at mine, and it just about killed half the party. I have made a list of individual games that you can put together in the form of a relay. But honestly, you could take literally any game mentioned on this site and incorporate it into a relay. Depending on how many people you have, you can break the group down into teams, and either each team member takes part in every game, or one team member volunteers to do each section. If you do it the latter way, the game moves a little faster, and you can have one big activity at the end where everyone is involved. I'd also recommend using something fun like a badge or a Hawaiian lei, in the colours of each team, for the competitor to wear during their turn. Or alternatively, the whole team can wear coloured bibs or even war-paint. Let the games begin.