I.G.
I think you are making to much out of this. My sister has 5 kids and when her youngest was born, we talked about not sending him any gifts until he's old enough to appreciate them. This last christmas was the first time I sent him something, he is now two.
For others who have had a baby I will also usually give mommy or family gifts, unless I know they NEED something for the baby. I hate giving little trinkets or useless toys that will just sit around and collect dust - and the same I would prefer not getting anything for my daughter over getting something useless, that now I have to find a space for to collect dust, so the person who gave it won't be offended...
Unless you're making it an issue, both of them will not even remember what they got or didn't get. Your older son will probably even just begin to really understand the concept of gift giving this year...
AND, if they send something for the family, that includes ALL of you, even your baby.
In my opinion it's just wrong to tie ones love (or perception thereof) to the amounts of gifts or money they send. If you see them interact in a differnt way with your second child, once he is a little older, then you can worry!