Help?

I would bring the kids along with you on your walks. Since they are 8&9 yrs old, they will enjoy a long walk in a park or playground. Think of other activities that you can do with them so you can burn some calories and they can play. Like going to play basketball or soccer in the yard. There's tons of things you can do with the kids .
As far as the fitbit, I don't have one. But plenty of people swear by them ! It motivates them to be more active and that's a good thing ! So you might love one ! There's fitbit groups and challenges on here all the time.
If your unable to join a gym for strength training could you pick up some weights to use at home ?

I am thinking bike rides? kids love to ride bikes with dad! but I am sure they would love to walk with you also.

Welcome. As a fellow Pats fan, I'll try to help you out.

50 pounds by September, while not impossible, is pretty daunting. Most of the reading I've done suggests no more than a 2# a week weight loss at most. Rather than set such a specific large timed goal, I would recommend starting smaller (for example lose 12-15 pounds in the next 2 months). It will make it easier to stay motivated if you set smaller goals and meet them.

What kind of job are you starting? Desk, active, what hours, etc? I know many people who get their steps in during lunch break (eat for 20 minutes and walk for 10). Also, depending on the job, I get up from my desk and walk around my office (it's a whole floor of a building) once an hour. Only takes about 5 minutes and it adds up, believe me. Also, park in the furthest spot possible from the front door of the office.

Take your kids on a hike. The weather is great right now, and it's quality time with them. Bring them to the park and play catch, or kick a ball around. It's a good idea to get your kids used to being active, and here's a chance to set an example for them early.

Bodyweight workouts are a great way to start getting stronger. There are a million free ones on the internet, and some great paid ones too (I would stay away from plyo and jumping stuff until you shed some weight). You can do this at home with no equipment (although I recommend a pullup bar with resistance bands). By the way, if you're looking to lose weight, you should not ignore lower body workouts. These are the biggest muscles in your body, and you'll burn a ton of calories working them.

Fitbits are good if you're tracking steps, and they work with MFP pretty well. There is a great community out there to help keep you motivated. That said, I wouldn't say they're as critical to success as a good nutrition and exercise plan.

You haven't mentioned anything about your diet. I can tell you right off the bat if you don't pay attention to this you won't have much hope of making a change. If you don't make calories out>calories in it makes no difference what workouts you do, you won't lose the weight. Since you're on Myfitnesspal I'm making the assumption you're already looking at this part of the plan.

Feel free to friend me. Good luck on your journey. Go Pats!

If you can't get to the park and they have bikes it's a good way too get your exercise and they enjoy it.. I used to do that with my daughter all the time when she was that age.. got me moving faster to keep up