Haven't RTFT - CBA sorry - but could you not just do it again, and get some photos of it (set the self timer....) and just use them? It may not have been the exact moment, but in a few years you won't care.
We had a joint Christening for our 2 DC in the mid 1990s, when they were 8 months old and about a year and a half old, and both of them were grumpy all the way through, not a single smile LOL. Just 😕and 😩and 😞Every photo of them just looking grumpy LOL! We had about 35 pics taken, (with our camera,) nothing professional, and when I showed them to friends and colleagues and neighbours a week later, some of them said 'oooh dear, don't they look miserable?!' 😆 (They were just overwhelmed I think, because about 30 people were there...)
I was quick on my feet and said 'oh this isn't ALL of the photos, I have some more to develop before I make up the Christening album.' Then what I did, I put the Christening gowns back on them, and DH and I put the clothes on that we had on for the Christening, and we took about 15 photos of us and our 2 DC, (several with the self timer of all 4 of us...) And on all of the pics (pretty much) they were smiling, and looked cheery. So I was able to mix them in. We went back to the Church and took a few outside, and had a few in our house where we came back to for a little buffet I made.
No-one ever knew (or cared) that there were 2 sets of pics, 2 weeks apart LOL, and the Christening album is lovely to look at. 