My DH technically paid for us to go on a Panama Canal cruise for our 20th anniversary, but we considered that a couples gift. I bought little things to make our trip special for him. I bought him a huge gift bag filled with new lingerie, chocolate, strawberry & other sauces
, a special $16 soap that I would never have bought otherwise, a speaker for his Iphone to play our wedding songs quietly (when we had a special dinner on our balcony), battery operated candles, etc. I also worked hard to lose 25 pounds for the cruise. He still totally one-upped me. He'd been so busy working to pay for the cruise that he hadn't bought me a gift. When we arrived at our cruise destination, he wanted to go shopping to let me choose a gift. I told him the only thing I really wanted was for him to quit smoking. Hey, it was worth a try. To my surprise he quit that day & is going on six years smoke free. I know that doesn't help you a lot, but it was huge for me. The funny thing is, we had this big 20th celebration, but didn't do anything for our 25th last October. Our DS graduated college this year & is going to grad school. That takes priority now. I'm okay with that. DH gave me the thing I wanted most for our 20th.
I haven't read all the posts, but I see you have older kids that could stay with family or friends for a weekend. Could you book a weekend getaway somewhere? A hotel in town (if that's all you can do), with a gift bag similar to what I gave DH, would probably be a hit.
For couples with kids still at home, an extended amount of time alone to concentrate on nothing but each other can be the best gift you can receive. Stay in. Order room service for breakfast & dinner & make it a really special anniversary.