You don't need to have an excuse. You have as much right to turn down an invitation as the others have the right to accept it. That is what invitations are for, so that you can ACCEPT of REJECT it.  No explanation should be necessary - ever.

Many years ago I was in your position and turned down the opportunity to do something with work colleagues.  I was given a formal invitation and I replied that I would not be attending. Every one of the others expected an explanation and I just said "Invitations can be accepted or rejected - I made my choice".  They were completely thrown off course - never having been given an answer like that I guess - but I stood my ground.  Sometimes that is the only thing we can do if we do not want to be coerced into doing what others want to do.

I believe that those in the wrong were the ones who felt I owed them an explanation.  I didn't and no-one should ever be made to feel that they must add an explanation to their answer.

First of all, you have nothing to be sorry about. Your English is flawless. ☺👌🏻

You do have a very good valid reason/excuse for not socializing with them, that is you have a family; a husband and child to be exact. 👨‍👩‍👧

Perhaps you should/could tell them that you treasure your days off (which is reserved) in spending quality time with your family. 💖 👨‍👩‍👧Plus that's the only time you have to catch up on bill paying, laundry, house cleaning, visiting the parents or other relatives, etc... Since you work (I'm assuming an 8 hour work day) and spend 2 hours commuting round trip, that right there is a good 10 hours per workday, which leaves you no time to socialize. 🛌🏻I don't blame you at all for NOT wanting to "socialize" with co-workers, even if you did like them. You see them all day at work, more than you see your husband and child on those days. 🙅🏻‍♀️Also, who'd want to spend 2 hours commuting on your days off, to "socialize", spending precious time away from you family and other commitments?! 😏Those co-workers must either be single, or don't have a close family relationship.Good luck!  Hopefully they get the hint and stop with trying to get you to go out with them! 🙄😃

Hello concerned one honesty is always the best policy just tactfully calmly respectfully let them know you prefer not to mix business and socializing outside of work keep it simple it’s not like you are obligated to them right? Pray for strength to say the right words and courage to stand by your decision if they are as professional as you are they should understand you have a life outside of work. 

Tell them that your "house arrest" ankle bracelet will report that you are not home at the predetermined time and you will be arrested.

Just tell them that family time is most important to you since you work, and that weekends are always planned family activity.

Your herpes is flaring up.

I'd just tell them you have a family obligation and can't join them. 

I agree with Jerry that you don't need to say why.

But if you do, just tell them the truth. Because you work, your family comes first when you have time off.

This reason alone will maintain your professional dynamic with them.

Maybe its as simple as you have just explained: The commute is just too much and you dislike it... tell them that!

Or, if that doesn't work, then tell them that your kid does some extra mural activities (baking, ballet, sewing, whatever) and you have agreed that on your off days, you will take her to her class and spend some parent-kid time together, which is a requirement of the course. Voila... you're out of meeting them for ever.

Tell them that your husband  won't let you go out  on weekends

 you're not going out for safety purposes ( covid)

or No one will look out for your kids etc.

You're busy on weekend because you have part time job