The couple are keen to head to the 'As Long As You Love Me' hitmaker's nuptials and Spencer has been doing all he can to get his name added to the guest list.
Spencer - who appeared on 'I'm a Celebrity ... Get Me Out of Here' with Hailey's father Stephen Baldwin - told Entertainment Tonight: ''I was telling my weight lifting coach ... God, I wish I stayed in more contact with the man who baptised me in a Costa Rican river on a reality show, because I would be going to the JB/Hailey frickin' wedding.
''I've been DM'ing him like, 'Hey, hey.' No [response] yet, but he's probably got a lot of DMs. No, I added him, I didn't DM yet. I was going to wait until there's a date for the wedding.''
Whilst Heidi added: ''We're so excited though. Last time we saw Hailey, she was like 12, so she's certainly grown up.''
However, the pair might not get the invite they want as it was previously claimed that Justin and Hailey want a small wedding.
A source said: ''They are discussing having a very small wedding. They want something private, intimate. Justin loves Canada and is at home there. It's a special place for him and he'd love to get married there.
''The marriage course is something which is encouraged and in some cases demanded by Hillsong pastors before they will marry you. Justin obviously has a past; he had a long term relationship with Selena Gomez, and he wants to go into life with Hailey with a clean slate. It is something they are both keen to do as faith is important to them and it will really help build a strong foundation for the years they plan to spend together.''