Hi there Greeycon,
I've not stayed that side of the lakes before so don't know any walks local to Irton Hall, but in relation to those you've mentioned........
Great Gable can be challenging to a reasonably skilled map reader in poor weather conditions so if there's no one in your group who map reads, make sure you pick a day when there's NO possibility of low cloud or better still, either learn before you go or don't chance it. Haystacks or Great Gable from Honister are faves of mine but again, can be tricky in low cloud or heavy rain if you've no map to go from.
Catbells is a straight up and straight back on the same path and sounds well within your capabilities, similarly Buttermere, if you mean around the lake itself. Both are very nice walks but each one will only fill part of your day.
If you're all inexperienced hill walkers, stick to simple walks. Catbells, walla crag via ashness bridge starting and finishing in Great wood car park is another decent stroll with cracking views. Low level walks around the smaller lakes (Buttermere / Derwentwater) are always a good option as there's little chance of getting lost, just bear in mind although they are smaller than some of the lakes, Derwentwater is maybe 9 miles round!
