As Barry says there is no guarantee of anything with chemo but I would say if your OH is tolerating it well and is fit and didn't get colds/flu easily before the treatment then it should not be to risky for you to go.
I went through chemo last year from July to Late October, only missed 2/3 days off work, still went out, traveled on Buses, Trains and Tubes, went to Big sports events and didn't get any sign of an infection. Okay so before my PCa Dx I rarely got ill and I suspect that helped.
The other thing I would say is that I found the support I got from friends and family when meeting them out and about was very uplifting and it would be a shame if you were to miss out on that. Weddings are the best of times for that. I was dx 8 weeks before my eldest daughters wedding and the encouragement I got leading up to that and on the day from everyone involved and there on the day was inspiring.
Going out and enjoying yourselves sometimes can be the best medicine.
Good Luck
Andy