First...a big congrats to you and your family on your new addition! Ahhh...morning sickness...I remember those days.
I went off WW a couple of months ago, stopped planning my meals and whoop! the weight started coming right back on. I've also got to get back on program. So, my advice, do try to stick with the meal planning and weekly weigh-ins, even if you're not on WW anymore. It will help you keep in the groove.
Get the other family members to help with the cooking by buying things that they can make s/a homemade pizza (pre-made pizza dough is cheap,) soups and veggie-based stews (very WW friendly,) create-your-own soft tacos, scrambles with eggs or tofu, beans of any kind (zero points,) etc. Let them create in the kitchen. If they complain, walk into the kitchen, drop to the floor like you're fainting and let them carry you to bed. They'll get the hint after a couple of these episodes.
It's your time to be a diva. I mean after all, how often do you get to do that?
As for keeping within a tight budget...make a list ahead of time. You don't have to plan every meal, but at least buy good, quality items to have on hand. I use the SAFEWAY ap and I scour their website, adding coupons and deals to my phone before I go shopping. It has really helped cut down our grocery costs. I"m sure that other big chain stores have aps too.
We stay away from processed foods as much as possible, except during the holidays when our guests expect their favorite "goodies." Otherwise, we go with fresh fruits and vegetables, which are usually way cheaper than meat or packaged foods. Send the DH, or another family member off to go shopping with your saved list and a total cap on the cost. (I like to send my DH with a credit card that is almost maxed out. If he goes over budget, then he's embarrassed when the card won't go though. I know, I'm mean sometimes. No 24-pack of beer for you, buddy.)
One last thing...go to some of the great websites out there for healthier recipes. Murphy224 and Farmquilter mentioned skinnytaste.com, which is awesome. There are lots of others too. Just do a search and you'll come up with tons of new and interesting foods to make. (That is, for your family members to cook. Not you...you'll be on the couch calling out instructions, as needed to the "chef" in the kitchen.)
The holidays are a difficult time to keep eating healthy. You gotta be armed and prepared.
Good luck!
~ C