You definitely should celebrate and you need something fun and interactive that you can enjoy together!! You need to reconnect - kids and life in general sometimes get in the way of remembering why you married and love eachother in the first place.
My suggestion is like a few others - do something goofy! minigolf is a good idea! bowling, a local fair/festival, an amusement park, a long walk at a local park (even better if it ends at an icecream shop!)... we have "hydrobikes" down by the niagara river near us that are fun - just little activities like that, doesn't have to be something big or extravagant. If its possible i love the camping idea (that's what we did for our honeymoon, its so great to just get away from everything together), but sometimes hard to work that out if you have kids in the picture.
If you're at a loss for ideas - pretend you're a tourist and look into whats fun to do in your area or somewhere close enough to drive. Sometimes there are very fun things that the locals overlook!
Dinner is always great idea, its nice to sit down after hanging out and wind down with some good conversation. but if money is tight, pack a picnic (or splurge on some takeout) and bring a blanket to a park if its a nice day!
congrats on your anniversary :)