Family Reunion Park Cookout Favorites
Fort Hunt park is nice; down the GW parkway midpoint between Old Town Alexandria and Mt. Vernon. There is a main pavilion to rent and smaller covered picnic areas. Not as many amenities as Burke Lake but there is a playground for kids, plenty of playing fields, and historic ruins to explore. Fort Ward park, in Alexandria City, right off 395 at King Street, is smaller but has several covered pavilions (for rent), plus a playground and more ruins.
If you want a covered pavilion in most parks, you'll need to reserve in advance and pay, otherwise open areas are first come first serve and you should plan to stake out your spot early.
My vote would be Burke Lake. Honestly, I use it for the hiking loop around the lake but it has so much more. There is frisbee golf, a carousel, train for kiddies, ice cream parlor, the hiking trail, a playground, and a mini putt putt. I think you can rent boats at the dock and you can fish. Heck, you can even camp. The only caveat, it's only free to Fairfax County residents these days. It's 10 per car, otherwise. If there are people in the reunion from FFX, pepper them in each car:) What's on the menu???