Hi,
As soon as you have to start paying for accommodation, trips can get expensive. You could always put the money into day trips instead. I go to Cornwall alot, and have some good contacts there for accessible accommodation, if you're interested let me know, and I'll forward the details.
The following suggestions are just for day trips, but as you live near me, I thought they may give you a few idea's.
Now, don't roll your eye's at me, but my first suggestion is
Skegness, it's near, has a good beach for the kids to play on, and has some rides etc. We took my daughter and her friend, and they loved it. I admit, the place is a bit tacky, but for kids, it's really good. It's probably best to go when the weather gets a bit warmer, as the wind of the North Sea can be a bit chilly.
Then there's
Twin Lakes at Melton Mowbray, There's loads to do there, and there are several large indoor area's as well. It is a bit hilly though, so you may need a hand at the entance. If you go a few times a year, buy a season pass, as this saves money.
In the summer, we go for a walk and picnic to
Bradgate Park, at the Newtown Linford entrance, it's really good for a bit of exercise, as the road which runs through it is smooth, but a bit hilly. On certain days of the week, blue badge holders can drive upto the ruins.
There's a place called
Conkers, which is an activity place which is good, and they have an indoor area as well. It's open all year round and is only five miles from Junction 11 on the M42.
There's also
Twycross Zoo which is just off the M42 as well, it's fairly flat, and good in summer, especially if you take a picnic.
If you're will ing to travel a bit further, you can visit
Drayton Manor, which is also off the M42 between junction 9 and 10. If you go to Tesco's, you can use your clubcard vouchers to buy entance tickets, which is a great deal.
Hope this gives you a few idea's.
Regards
Simon