What activities do your boys do?

At that age both of my ds started Beavers which then led onto cubs. They had lots of great experiences.
They both swam.
That was it when they were really little.

Later...football/rugby/basketball, guitar/drum lessons, whatever after school clubs were on offer (gardening/art etc)

My nine year old rides, goes to drama, does piano and swimming. My 4 year old is starting riding, has just started piano lessons and does a little football class which he enjoys. My nine year old has tried loads of things. I think it's important to give them lots of options so they can pick the ones that fits them best.

I have two boys, now 11 and 7.

Swimming has always been our non-negotiable and they both still do it, 11 year old started very slowly and hesitantly but is now reasonably good and loves it. DS2 is still at the learning stage but making progress. Both have lessons once a week.

One does music and the other guitar, both do Stagecoach - youngest started it in early stages (4-6 year olds I think?) and elder joined age 9 and it's been amazing for him, brought him out of a lot of his shyness. Both get a lot out of it.

Elder does football (training + match), younger does a language club at school, chess and drama clubs. Elder used to do gymnastics but has ditched it. He started ukulele in Reception but I don't think he was ready for it, plus didn't do well in a group session which is what was on offer.

Tennis
Karate
Violin (just started age 9)
Swimming
Bouldering ad hoc

Judo. Swimming when younger.

My son started dance at 2:5yrs old, he now 8 and does six dance classes a week( more than one style of dance on some days) plus swimming, cubs and Jujitsu.

At 4 DS2 started Stagecoach and bloooooody loves it! He’s 5.5 now and got a big part in the show they’re working on now #proud ☺️ Also does swimming.

At 4 DS1 started ice skating and did it for a couple of years, he’s very good but not commited.

Hes also tried tennis and currently does football. Has finished swimming.

My 9 year old does a guitar lesson, cubs and two different youth clubs. He also does a sports club at school, a different one each term usually. Monday he will start dodgeball. He also did a weekly swimming lesson but stopped when we moved and he now attends a school that has a swimming pool and he does swimming lessons as part of pe.

My nearly 5 year old doesn't do anything but has mild additional needs and is very much into being at home with just his family.

Oh yes, and gymnastics! DS isn't a team sports fan, but enjoyed gym for several years. Now just swimming and lots of music (he's 13).

At school or preschool? Options usually open up when they start school. But given what you've said, I'd look into local options like dance, drama, music groups (bit young for 'serious' children's choirs but there's often some kind of music group that tides over between preschool classes and joining a choir at 7ish). Find a few options then discuss with DS what he'd like to try. I'd add one at a time and see if he's still wanting more after a term or two.

Instrument wise if you think that's something that might appeal at some stage, maybe listen to and watch different instruments and see if there's something particular he fancies. Depending on the instrument and local teachers it might be he could start soon or better to wait a few years. Piano and strings seem to be most common for young starting. But also only if you have good local teachers who like that age group, teaching 4 yr olds is different from teaching 8 yr olds.

Popular things in DC's classes were swimming, beavers at whatever age that starts, team sports (football/rugby/cricket), music, drama, kung fu

He's 14 now and has trimmed down his hobbies but we have had:

Judo
Street dance
Rugby
Football
Ice skating
Violin
Gymnastics
Drums
Bass guitar
Golf
Fishing
Athletics
Cricket
French lessons
Spanish lessons
Maths club
And probably many more over the years that I've forgotten!

He still plays his instruments bar violin, plays/trains at Rugby every weekend, regrets giving up gymnastics, plays cricket in the summer, has no real opinion on golf, is still hopeless at maths and his Spanish moves along at a glacial pace...

We may do riding lessons this year just so he has that skill. Also tennis.

I've always tried to do a broad mix and never insist he sticks at something if he's clearly not enjoying it (except maths!). He's allowed one "A&E" sport at a time, so he chose rugby over ice hockey (thank god).

At 4.5 I would say gymnastics if your son likes a run about, mine loved flying over the box from the springboard as he had no fear at that age! Personally with swimming I went for water safety at that age: enough locomotion to swim to the edge of a body of water and techniques to pull themselves out of said water as opposed to actual lessons until he was 7, he then got really excited chasing fish whilst wearing a snorkel on holiday and essentially taught himself.

Guitar and athletics

He did swimming and football but now does football a couple of times a week and guitar, one lesson at school and an evening one elsewhere. That’s enough for him (and us!), he’s 11.