DH and I have gone to where we mostly just give gifts to the children in our family. Years ago, we explained to our parents/siblings/grandparents that it seemed ridiculous to be exchanging gifts with other adult family members when all of us could go buy anything we really wanted or needed. Also, shipping was costing as much as the price of gifts in some cases! We told our parents that they could still get something for our kids, but we would prefer that they try to limit themselves as the kids had more than enough. We send out family photos for Christmas, so all of the adults are still getting something from us.
If I were you, I would just tell your kids that you would like to just give presents to the grandchildren at Christmas and Birthdays from now on since you're preparing for retirement. And that you'll be toning down how much you spend on the grandkids too.
As for in-laws and others, just tell them (ahead of time) that you'll be trimming back on Christmas gifts. It's not impossible to cut back. You just do it. Spend less per person on gifts -- set a limit. For my children, we spend no more than $200 on Christmas gifts and that includes stocking stuffers. For neices and nephews, we spend no more than $20 each. Right there, we have spent $500. Including gifts for DH and I, a few housewarming gifts, nice family portraits, and money for holiday feasting, our budget is around $1200.
As we've gone to spending less, we've also tried to get back to doing holiday activities as a family so that we've replaced some of the gift giving with other activities: decorating the tree as a family, decorating sugar cookies, going to a Christmas concert, going to church service, etc... We're really trying to get back to "the reason for the season" and away from the biggest day of "gimme, gimme, gimme" of the year. In that vein, you and DH could replace some of the gift spending by purchasing Grandparent memberships for the local zoo, aquarium, museum(s), and/or season tickets to the theater/symphony. Instead of spending money on "stuff" for the grandkids, you could spend your time with them.
