Did they say they wanted to pay for the wedding? I mean they're not actually "paying for the wedding" if they're not covering it all, they're "contributing". That's totally fine and also generous, but not the same.
We paid for our wedding (60 guests). It sounds nice to have someone else pay but after years of reading Mumsnet wedding threads, I've come to the conclusion it's a minefield, unless you have no strong ideas on what you want. Once someone pays for something, they want something. It can be a say in colours, guests, location, a type of flower, food..anything. And the people who get extra excited and want a big wedding, well, nice, but it's not their wedding.
It's also a bit much to want a big wedding and then expect the couple of inlaws to stump up the rest. They really don't get to decide how other people spend their money/contribute to the wedding!
How about going back to your original plan, but having a specific thing they can pay for if they want to?
And while this may be a time when you don't want to rock the boat, you don't want to upset future inlaws etc, it's also important to draw boundaries. Honestly, how the wedding planning with family goes impacts the beginning of your marriage and can set the tone for years ahead. I don't mean being rude, but you and DP are the couple, it's your wedding and you shouldn't be agreeing to anything simply to not cause problems. You'll never get this time again. You can't expect to get a "do over" if/when any kids you have get married! 😉