I'd say nothing is more important to your children than healthy parents. If the marriage can be saved, it's better for everyone - economically, emotionally, everything. You have to decide that you are more important than your activities. Take clothes to the consignment shop, walk dogs and take in mail for vacationing neighbors, water plants and weed gardens.
You can find more reasonable choices in every area, and take all of that money ($20 here, $15 there) and put it in a therapy fund. I don't know how old your kids are, but they can benefit long term from having small jobs to help pay for their extras (field trips, extra curricular activities, everything they "just gotta have" in terms of clothing and backpacks and electronic gadgets and movie rentals. Kids can learn to economize. They can do jobs in the neighborhood depending on their ages - run a lemonade stand (and they pay for the lemonade, they don't just keep all the income), have a yard sale where everyone gets rid of 25% of their stuff,
Cut your cable bill by getting rid of expensive packages. Cut your heating and AC bills by changing the thermostat by 2 degrees either way. Shop in bulk. Stop with designer labels for everyone. Cook at home using real ingredients instead of eating out. Give your kids tap water in reusable bottles (stainless steel best) instead of juice drinks or bottled water (a HUGE budget-buster as well as an environmental nightmare). Make sandwiches instead of using pre-package meals. Get cheaper haircuts. Nobody gets massages or facials or manicures, no matter what.
There are less expensive counseling services available through the clergy - free if you are a member or a regular attendee, and often if you are searching for a house of worship. Some are available also through the town's department of family services. Usually those are sliding scale though, and if you have a high paycheck and a lot of amenities/privileges, you won't qualify OR you'll be taking the slot from someone who really can't afford it.
Finally, budgets are not set in stone. They are subject to revision if circumstances require it. If you had a financial emergency (someone got very sick, you had a devastating fire, the furnace blew), you'd cut something out. You'd also adjust if your refrigerator quit or your dishwasher overflowed or your car transmission blew.
Therapy money is not EXTRA. It's essential. If you want the best for your children, you will spend money on what keeps them secure and in a whole and happy home. If your husband really needs convincing, tell him you can economize by getting one mediator instead of 2 separate divorce attorneys, and a financial planner to help you figure out what size apartment each parent will need to take the kids during your half of the visitation. If you two don't make it, all those essentials (tuition, vacations, activities) are going to be canceled outright anyway. They might as well learn to do without a few small things right now, rather than grow up with a sense of entitlement.
And your kids will get into better colleges if they learn to work part time, do charity work, and give of themselves - not if they go to only the best schools and have a long list of activities. Colleges want kids who work and appreciate things, not kids who got handed everything.