Your boys are about 20-21 months, right? There's not a whole lot out there for kids that age, just because they do usually require one-on-one attention for most activities.
Have you checked with your local library or bookstore? Many offer an "all ages" story time, occasionally with activities afterward. Our library has one day a month for the kids to come in and dance.
What about a parents group? The community I live in has a parents center and they have set up an indoor playground for kids up to age 5. It's only open during the winter, and it's not free, but it's worth it to have a place to run around. Some shopping malls now have play places like that in them, too. If you can go before it's too busy (and it seems like you need to disinfect the climb on toys) it's not bad. It's not really an activity you do together, but it's a change of pace and something to talk about for a few days afterward.
There's always the option of signing up for one of these activities and then swapping out who goes and having dh or someone else watch the other child. In another year or so you will have a lot more choices.