Lucky you've got your husband to go along & help!
>wear the baby, sling or otherwise, keeping hand free for preschooler
>wait until the last minute to get on the plane.
>keep the baby awake so he/she will sleep on the plane, nurse during take-off & landing to alleviate ear issues.
>car seats aren't much good on planes (mine would never stay in it), if you can check it, do so; otherwise look for options in GA to rent one, or borrow from a buddy (tho' I know this isn't exactly on the up 'n' up, could purchase one from WalMart or similar then return when the weekend is over)
>snacks & sippies for sure, and I second the new toy idea, magnetic shape toys are awesome for travel, keep'em squirreled away until kiddo gets pretty bored
>also let the preschooler pack their own little backpack for the flight, allow them to be involved in the decision making, i.e. snacks; and talk-talk-talk about what it'll be like for the trip pre-, on plane, & post-plane, what you expect of him/her, get some plane travel books from the library to prep
>just understand that it's a LOT for them, and it's a LOT for you...if you need a break, take one, they're bound to have a meltdown at some point (they're little) but mamas don't have to take the same head trip...we're supposed to be the grown-ups!
Good job mommin'!