Delavallée is a product of the academies of the Belgian clubs CS Entité Manageoise and Mouscron. On 11 June 2021, he signed his first professional contract with Mouscron. On 17April 2022, he debuted with Mouscron as a substitute in a 2–0 loss to S.K. Beveren in the Challenger Pro League. On 19 June 2022 he transferred to Royal Charleroi on a 1+1 year contract, and started playing for their reeserves. On 3 April 2023, his contract was renewed an additional year. Shortly after on 4 July2023, he extended his contract until 2025 and started playing with their senior team. On 14 December2024, he again extended his contract with the club until 2027. In the second half of the 2024–25 season he was started playing as their starting goalkeeper.
On 21 October 2021, Delavallée debuted with the [Belgium national under-18 association football|football team|Belgium U18]s for a friendly against the Czechia U18s.
Personal life
Before committing to football, Delavallée was a renowned player for the Belgian game Balle pelote.