Alison, I know you want your son to make up his own mind on the breakfast thing but I think your son was wanting you to be more open with him as to how you really felt from what he replied.

"Then he went upstairs and siad he had just given me the chance to say I didn't want him to go. I pointed out that it could also be construed that I had told him I didn't want him to go. I still don't know what he will do. I will be very hurt if he goes but will not say anything."
I know you said you wont hold it against him IF he goes but I think the reality may be different IF he does go--you may not mean to but your body and facial language will give it away especially as your daughters have decided against going.
I cannot see why you couldn,t have just said
I would really like you to spend the whole day with me but if you just go for breakfast and come home after thats fine, but it's up to you.
All the repeating and then to say it could be construed as meaning that you didn't want him to go IMO was uneccessary, more like what the old AJC would have said.
Boys are not on the same page as daughters when it comes to things like Mothers day.
What will you be doing for the day if he goes or if he stays.
Don't make it an issue or a son v daughters debate.
After all he probably wouldn,t get out of bed til lunch regardless of the day.
This is just my opinion having sons and a daughter.