I am so sorry about the death of you FMIL. My FFIN passed away two years ago so I undersatnd the stress that can happen. It's a helpless feeling, you want to take away your FI's pain but there is little to do except be supportive in a sad and hectic situation.
I think you and your FI need to sit down and weight out the pros and cons. If you both want to go ahead with your plans, then do it. Don't let others come in between you and your FI on your day.
I agree Amarillis too! You need to have a real heart to heart with your dad. Also talk to him about your brother and that is your wedding.
I second it...no bridal party. It's perfectly fine. If your MOH and his BM can't but their drama behind then screw them. I'm sure you FSIL and BFF will understand, they can still come if they want but less worries overall. My MOH can't make it so I just said not wedding party...less worries...less drama.
Good Luck