My son has been competing in triathlons since he was 4yrs old, he's npw 10 and going to travel to the Nationals for the first time this year. He first rode on his BMX bike and graduated up through various sizes on a Frog racing bike up to his latest racing bike from HUPcc in the UK

The bike has a single front chainring with 10sp shimano at the rear (11-34)

The chainring is 38T

Would moving up to a 40T chainring make a signifiant difference? I'm not sure what the bike courses are like at the nationals for the kids in the 7-10 age group, whether they are hilly or flat

Any help would be appreciated

Thank you