I swaddled my 5 year old until well after he was old enough to "break free" - which he often did, but would actually bring me a blanket when he wanted to be 'wrapped up'. Just use a regular baby blanket, instead of a premade swaddler - make a diamond by folding one corner part way down, then left side over left arm, under right pit, feet up and over legs to the right, then right side under or over left arm. It doesn't have to be a tight swaddle - just a little resistance to the flailing. He'll be breaking free soon - and that seemed to make the transition easier for mine.
FWIW, he spent 80% of the time that he wasn't napping in a sling, hip dysplasia (shallow hip sockets that may in part be related to lots of time spent with the hips straight) really wasn't an issue for him. My 2 year old did not like to be swaddled, still spent a LOT of time in the sling, and DID have mild hip dysplasia - so go figure.
S.