I am trying to spend extra time with them but usually they all like to do their own things and have me just be there somewhere.
You're in a tough spot. You put your life on hold, more or less, always there for everybody, and now they're uncomfortable that you want something for yourself. No one to make their sandwiches anymore. Fold their laundry. Wash the bathroom.
Hand them a broom, and give them a choice. Attack the kitchen floor, or attack you. Then show them that housework is not as painful as they once thought. They need to learn to not expect someone else to handle tasks they consider beneath them, this is a matter of respect of self and fellow. They also need to let you evolve beyond the role of Mommy, the role of Food-Lady. They need to get over wanting you there, just because they, uh, want you there. Tell them aikido helps you become more
you, that it is actually giving you better skills as a person, and therefore as a Mother.
I am blessed, as my girlfriend trains in aikido, so no issue there. As for Hubby, I can imagine a couple of reasons he might feel alienated or left out. If I didn't train, and it was introduced to me through a seemingly over-enthusiastic girlfriend I would likely feel somewhat left out, confused, a little anxious.
1) we would be apart
2) you would apparently be greatly enjoying yourself outside of my presence (meaning you enjoy my absence)
3) The comparison angle; how do I compare to the dojo guys, can I compete, can I show that I can protect the family
4) Traditional roles; (similar to # 3) I should be enough to protect you, and I certainly don't need you to protect me.
5) general martial arts inspired uncertainty; what is it, can't I protect myself without it, what if I should be doing this?
6) a genuinely fair-share of home duties.
Anyhow, I hope it works out for you. Bring lots of assurance, and lots of gentle understanding of husband and kids perspectives, which may be delicate even if they are also a little on the selfish side. Even if all you get out of aikido is increased fitness, it is ultimately a benefit to them.