What an odd phrase! I think it means "If freestyling is more to your child's liking, you should choose..." So far as I'm aware, freestyling is a way of swimming (= choose your own stroke; front crawl is the fastest) but I suppose it can be applied to other practices like painting without a preliminary sketch?
Yes, freestyling can be a fairly general adjective meaning not following set rules or guidelines. You make it up as you go.
In regards to "more your speed", I think it is ultimately connected to speed and intensity, at least originally. When participating in some activity, some people aren't suited for the highest, most intense, most challenging level. For instance, at ski resorts, ski runs are marked by difficulty level with a code like a black diamond for the most difficult. They are the steepest and trickiest and require you to have much greater ability to control your speed and turning than lesser runs. Some people don't have the skills to go that fast safely.
So "more your speed" ultimately indicates that sort of suitability. But it has become generalized to include the idea of a preference as well as skill and what sort of level of an activity suits you best. And that's especially true with children, who have all different levels of skill and interests as they mature.